There seems to be achievements in the gog version as well. Even without logging into bethesda.net they unlock. They don't seem to be in the main game directory, as I uninstalled and reinstalled the game to check. Kind of an interesting choice, haven't found where they are stored on my machine yet.

Update: Found the achievements file. Seems to be saved in the saved games folder in C:\Users directory. A neat piece of info for anybody curious.

These ingame achievements don't seem to work. They do properly register during the game, but they don't seem to be permanently recorded :(

If there's anyone here looking for a way to turn off damage indicators in the game (the red stripes around the crosshair) then I found the solution.

Simply extract file "pakMOD_damage_indicator_off.pak" to baseq2 folder.

https://steamcommunity.com/app/2320/discussions/0/6812310007737233326/#c3808409598687117116

The title tags in the ogg files for Quake Enhanced (setup_quake_enhanced_1.0_(60828)) appear to be incorrect.
For example, track02 is the Quake Theme song, but it is incorrectly tagged with the title as "Aftermath", while track03 is the actual Aftermath song, but that file is tagged as "Damnation". Other tags seem to be incorrectly tagged too.