lol. thanks, buddy! I had checked on discord in the meantime and found the same entry. FreeTrack is something else though.
I've still got it to work by copying scptrackir64.dll and scptrackir.dll into:
and then forcing Wing Commander Saga to use \FreespaceOpen\bin\FSO-21.4.0\windows\x64_avx\fs2_open_21_4_0_x64_AVX.exe . You can do that in Knossos / Options button of the mod / FSO Settings / FSO build.
Now what I don't understand which executable (the "mod default") WGS used before I forced this on it, if not any from the four directories above. Well, so be it. It works.