I tried what I think is the same way I installed it in the Steam version, but when I try to run it I just get a couple quick windows that close immediately and then nothing happens. Any help would be appreciated.

Edit: The window that closes is titled SDL_app I think.

You are awesome, thank you! One more question, how do you get the demo modes to play as in the original running quakespasm in the gog version? I know how to do it in Steam version.

Cool, glad it worked! Are you talking about the demo recordings that (in the original Quake) automatically start playing when you launch the game?

Hmm. I haven't tried to make Quakespasm do that, but my guess is that you could put this line in your autoexec.cfg file: startdemos demo1 demo2 demo3

Or if you don't want to have an autoexec.cfg file but you are happy fiddling with command-line parameters, you could add this to the Quake command line: +startdemos demo1 demo2 demo3

I'm not 100% sure that will work because I don't know how Quakespasm is stopping it from happening normally.

(If that is what you are talking about, and that solution doesn't work, I can experiment with other solutions later.)

I found the solution to that problem as well: https://www.gog.com/forum/quake_the_offering/quake_the_offering_music/post80

Right-o. I had forgotten about the "-fitz" option.

Just FYI, using the "-fitz" option has a few other effects too. I glanced at the QS code and it looks like it makes these changes:

- Disables loading "quakespasm.pak". That gets rid of the new console image, map entity fixes, and the Quakespasm default config.

- Plays demos on startup again. (Looks like maybe the startdemos command is normally just generally disabled in Quakespasm? ... and this restores its functionality.)

- Will draw the credits placard with "Press y to quit" when you quit the game, instead of just quitting immediately.

- Removes some things from the singleplayer scoreboard (what you get in the statusbar when pressing Tab): skill setting, level name, and mapfile name

You might or might not want to be disabling all those things. Some of them are nice. :-) Although on the other hand, removing those changes also gets you closer to the original Quake behavior.