I see the logo spin up and everything looks good, but as soon as I hit (A) it crashes.

Terminal is spewing about glDrawBuffers

$ ./Celeste64
Celeste 64 v.1.0.0
Foster: v0.1.13
Platform: Debian GNU/Linux 12 (bookworm) (X64)
Framework: .NET 8.0.0
SDL: v2.28.5
OpenGL: v4.6 (Core Profile) Mesa 22.3.6, AMD Radeon Graphics (rembrandt, LLVM 15.0.6, DRM 3.49, 6.1.0-9-amd64)
FMOD Bindings: v20218
FMOD: v20218
Loaded Bank: /home/computermouth/downloads/Celeste64-linux-x64/Content/Audio/Master.strings.bank
Loaded Bank: /home/computermouth/downloads/Celeste64-linux-x64/Content/Audio/Master.bank
Loaded Bank: /home/computermouth/downloads/Celeste64-linux-x64/Content/Audio/music.bank
Loaded Bank: /home/computermouth/downloads/Celeste64-linux-x64/Content/Audio/sfx.bank
Loaded Assets in 715ms
GL (ERROR:HIGH) GL_INVALID_OPERATION in glDrawBuffers(unsupported buffer GL_COLOR_ATTACHMENT0)
GL (ERROR:HIGH) GL_INVALID_OPERATION in glDrawBuffers(unsupported buffer GL_COLOR_ATTACHMENT0)
GL (ERROR:HIGH) GL_INVALID_OPERATION in glDrawBuffers(unsupported buffer GL_COLOR_ATTACHMENT0)
GL (ERROR:HIGH) GL_INVALID_OPERATION in glDrawBuffers(unsupported buffer GL_COLOR_ATTACHMENT0)
[...] goes on forever, til I hit the A button and crashes [...]

exit code: 0

ldd also shows maybe a missing dep.

$ ldd libfmodstudio.so

    linux-vdso.so.1 (0x00007fffde8e0000)
    libfmod.so.13 => not found
[...]

Tried symlinking the local libfmod.so, no change. Went to fmod's site to download their libs, as suggested by the debian wiki page, but it's behind a login, then I quit.

The windows client crashes the same for me under WINE.

Thanks for the info. I'm away from my linux pc right now but should be able to fix the symlink issue with FMOD soon.
Regarding the main crash though, it looks like an OpenGL issue. I'll look into resolving that, thanks!