The crash seems to happen randomly. Where I see it happen the most is on the mission Bearbaiting. I am playing using the MediaVPS hi-res textures mod and the hi-res HUD assets mod. I can see if it happens with retail assets without mods. The crash occurs when the Sathanis jumps out if I am looking at it when it jumps. If I'm not looking at the ship when it jumps, the game does not crash.
Thanks for finding a reliable repro. By "looking", does the crash occur if the Sathanas is anywhere in view? Or only if it's in your reticle? Or only if you have the Sathanas targeted? Does the crash occur if the Sathanas is targeted but out of view? If the crash occurs specifically when you have the ship targeted, does it occur if you have one of its turrets targeted? Or if you have one of its subsystems targeted?
Basically, the more precise you can be on when the crash does(n't) occur, the easier it'll be to track down, although you already have a good start.
To make repro faster, you might try speeding up the game (or as the FS2 manual says IIRC, "increase time compression"). I think the hotkey is > but I forget. However, I don't know if doing that will make repro less reliable.
I have not built FSO myself. I'll look into what's required to get a debug log. If you need a core dump I may need to reconfigure my system to allow larger corefiles, since I think the non-debug coredump is already over 2 GB.
I take it you're using the fs2_open-appimage AUR package
? I don't know anything about package management in Arch, but is it possible to build the package with a Debug build configuration? If the game runs too slowly with a Debug build, try the FastDebug build configuration, which is defined in FSO's CMake scripts.
I don't know what's required to get a stack trace on Arch. Perhaps a core dump isn't required.
The only case I can think of offhand where a core dump might be useful is if having both fs2_open.log and a stack trace ends up not being enough info to figure out the root cause. In that case, it might help if you could inspect a core dump in GDB or similar for, e.g., values of local variables at the time of the crash. But hopefully we won't need to get into nitty gritty like that.