I think the most important things have been adressed but I'll try to go over everything you mentioned for completeness sake.
So. I open it up and Mantle -- which is in my FS2 folder along with a billion other mods -- is nowhere to be found except as a tile in the "explore" category. Installing that would presumably just download the old version that I released last year, which I don't want to do because it would be pointless
This already presents a problem: Someone already uploaded your mod and if you upload it yourself, there's going to be two seperate entries for Mantle on Knossos which is going to be VERY confusing. In this case it was Novachen who later deleted it for unrelated reasons. This also explains why it later vanished.
and I don't want to test because downloading things with Knossos doesn't work.
This is a serious issue which we'll have to resolve because using Knossos is pointless if you don't download anything. It's simply not going to work.
The only mods that are installed are a couple that I think I installed last time I tried to use this thing, before I gave up and deleted some of the Knossos files so I could actually use a functioning launcher again.
Which files did you delete? If you deleted anything outside of
%APPDATA%, there's a good chance you broke something.
Now there's also this other Freespace Open folder alongside my FS2 directory, which IIRC was also created during my first Knossos install.
Where is this folder? Are you talking about
%APPDATA%\HardLightProductions\FreeSpaceOpen or another folder? The former is created by FSO.
I'm guessing that this folder is the one you selected when you installed Knossos. The first time you run it, it sets up everything it needs and asks you a few questions. One question is where to install mods. Since Knossos uses a folder structure which is different from other launchers, it needs a new folder and can't use your old FS2 installation. The new folder structure is
necessary for a few things that Knossos does (among them TC support, supporting 32 and 64bit builds side by side, etc.).
It has folders for the few mods Knossos registers as installed, which I think contain all of the necessary files for those mods. However, it doesn't contain any FS2 executables, FRED instances, or anything that looks like it might be a dedicated launcher. I have no clue as to the purpose of this second folder, beyond the misdirection of hapless modders.
That folder should contain the FS2, temp and bin subdirectories. The bin folder contains all installed FSO (and FRED) builds, the temp folder is used for downloads and the FS2 folder contains the installed mods. If you install TCs, they'll also get their own folder here.
A dedicated launcher would be pointless since Knossos is already a functional launcher.
So at this point I don't even know where I should be looking. Most of the features of the launcher I'm used to seem to appear in the options menu, except there's no way to, y'know, actually launch it -- except by selecting a mod from the list.
That's the point. You click on the play button for the mod you want to play. After that (if everything was installed properly), FSO launches and everything from there is the way it used to be. Command line flags work differently in Knossos compared to other launchers. Instead of having profiles (like wxLauncher), Knossos stores the flags for each mod. You have a global flags section on Knossos' settings screen which allows you to set global defaults. These are combined with the settings the mod dev set when uploading their mod to build the mod's command line flags. Finally, you can edit the flags for each mod by opening the FSO settings screen (Home tab > dropdown for the mod > FSO Settings). This overrides all other flag settings. The idea is that you can have a global set of flags which affects all mods, inexperienced users get a nice default setting from the mod dev and experienced users can tweak the flags on a per-mod basis.
Anyway. So I tried moving Mantle and its dependents into the Freespace Open folder, hoping that Knossos would register them as installed.
This doesn't work since Knossos uses mod.json files instead of mod.inis and a different folder structure.
(This appears to have made Mantle vanish from the list of installable mods, which is weird as hell -- presumably some name-uniqueness thing? That or it was removed since I last saw it and I'm just not remembering correctly.)
As mentioned above, Mantle was removed by Novachen who uploaded it before and thus is completely unrelated to anything you did.
It didn't make Knossos register them, but it did let me run Mantle with the command-line flags. Unfortunately the game shat itself and closed as soon as I loaded a mission. Apparently it couldn't find any of my custom assets, despite they and their tables all being right there in the folder that I moved.
As I pointed out above, Knossos uses a different folder structure. I'm not sure where you moved your mod files but chances are that FSO was looking for things in the wrong folder.
(Something similar happened when I tried to run FRED from my FS2 folder -- opening a mission from Mantle resulted in a bunch of errors and half the ships getting turned into Ulysses because somehow it couldn't find my models.)
Due to the different folder structure, manually running FSO or FRED unfortunately doesn't work anymore. You have to launch them through Knossos. Additionally, in the most recent version of Knossos it doesn't even use the cmdline.cfg file anymore which means that manually running FSO or FRED will completely ignore any mod selection or cmdline flags from Knossos.
So I moved Mantle's folder and its dependents back, saw that other thread on using the "development" tab to create a mod for this purpose, and tried that.
This is the intended way and would've saved you a lot of frustration.
I managed to make a mod pointing to Mantle's ini. It yelled at me when I tried to put bpcomplete and mediavps_2014 as dependents. I was hoping that wouldn't amount to anything; I was incorrect.
Errors or warnings from Knossos usually have a reason. If you see one and everything works fine, you've found a bug. What did the error message say?
But that doesn't help anyway because once I put in the settings and launched it, it just gave me retail FS2. Presumably it can't find bpcomplete or the mediavps. Aaaand that's where I am now, having finally gotten sufficiently annoyed about this to go on the internet and rant about it.
Apparently, your mod's dependencies weren't setup correctly which resulted in FSO not using/finding them.
So. Here's what I think is happening:
When Knossos installs a mod, it installs it into the new Freespace Open folder. This installation contains unique architecture which can't be replicated by simply moving a preexisting folder from the old system into the new directory.
Correct.
Therefore the way to link an old mod to Knossos -- other than building said architecture from scratch, which I have no idea how to do -- is to use the "development" tab to create a shell mod, containing the necessary architecture, which points to the old one.
Partly correct. Building the folder structure from scratch is easy but creating the mod.json file can be complicated an error prone. Using the dev tab in Knossos is way easier and prevent most common mistakes.
The new mod is neither a shell mod nor does it point to the old folder. Knossos copies the mod files from your old folder into the new folder and tries to convert as much of the mod.ini contents as possible. However, this process isn't simple and tends to fail (which you apparently experienced). In my experience it's easier to create a new mod in Knossos from scratch and copy the files over yourself. Also, Knossos extracts your VPs if you use the automatic mod.ini import IIRC.
But, presumably, Knossos doesn't know what to do with further dependencies if they rely on mods it doesn't recognize.
Correct.
So if I wanted to run Mantle, I would need to create a Knossos mod pointing to mediavps_2014, then create a Knossos mod pointing to bpcomplete and dependent upon mediavps_2014,
ABSOLUTELY NOT! This will cause issues for everyone involved later on and is unnecessary work. You're supposed to install the MediaVPs and Blue Planet Complete through Knossos. That's the only way it can guarantee that your mod works for everyone later on since it can guarantee that everyone is using the same files and setup.
This...just... It makes me think this is a system specifically designed to generate cruft, and I have no idea why. I can only guess that the intent is to create a cleaner mod installation system, but in this case, at least, it's done the opposite.
I think you got a completely wrong impression which seems mostly due to the fact that you're trying very hard to use your existing FS2 installation which unfortunately isn't possible with Knossos. Knossos is a self contained system which makes it more robust and easier to use for new people. An unfortunate side-effect is that it's not compatible with mod.ini files, existing FS2 installations or other launchers.
The new MediaVPs won't download. They got stuck at 95% after like three hours*,
You can click the blue "Installing... 95%" button and receive a more detailed view of what Knossos is doing right now. Can you please post a screenshot of it and/or your
%APPDATA%\knossos\log.txt file? That would help me figure out what is causing your installation issues.
and then when I tried to cancel (because it doesn't let you close the program while there are processes running) it stopped responding. Gah. At least it doesn't keep running in the background after I close the window; those are the worst.
I just went through the related code. If the download is stuck, aborting it can apparently lead to Knossos hanging since it waits forever for the download to abort. I'll see if I can think of a proper way to fix this. My guess is that the connection to the download server was interrupted and never timed out (although it should).
*I have a fairly bad internet connection at the moment, so that might just be how long it takes. Still, I'm not sure.
This reinforces my suspicion that the connection was interrupted which means that the download would've never finished anyway.
So...I'm genuinely not sure what I'm supposed to be doing here. Is there a big link to a guide somewhere in one of the release threads, [...]
No, however a lot of these questions have come up on Discord or in the Knossos thread where they were discussed and resolved. At some point it was proposed to write a guide for Knossos but that effort died. I've tried to make Knossos as self-explaining as possible (i.e. if you create a new mod you should see a help text explaining what packages are and how they work).
But, in my case -- I need some idea of what's going on under the hood, because I have to make sure my mod isn't broken. And...this whole new system is making that process a giant pain in the ass.
It's supposed to do the opposite. IMO most of your problems are a result of you wanting to do things manually as you've done them before instead of using the dev tab or asking for help.
I hope I've answered most of your questions and that you'll ask for help earlier next time you run into issues with Knossos. (If you had asked for help when you noticed that installing mods didn't work, we might've avoided much frustration.).
I can't fix bugs that I don't know about.EDIT: wxLauncher should continue to work in the future unless the SCP team decides to introduce a new breaking change. In fact, older launchers should work fine with recent nightlies even if you use the latest wxLauncher or Knossos.
Regarding the download links, here's a list of all publicly available mods on Knossos with download links:
https://fsnebula.org/mods2nd EDIT: Forgot to respond to something.
[...] it doesn't let you close the program while there are processes running [...]
If it did, chances are you'd end up with a corrupted install since you would have interrupted it in the middle of installing a mod. To avoid such problems, you can only quit Knossos after cancelling such tasks which takes care of the cleanup. I agree that it'd be better if you could close it and have Knossos automatically cancel any running task but that turned out more complicated than I'd like since I never considered this scenario when I designed the task system.