KQ8 is crashing to desktop every time before the menu.
I did try Nicode's fix for getting the game to launch at all.
Now it just crashes right after showing the start screen and a black small window instead.
The error message only says that Mask of Eternity has stopped working.

I'm trying to run it on my GPD Win.

A log file (Mask.kq8fix.log) and/or crash dump (Mask.kq8fix.dmp) would be nice. See the notes at http://kqmoe.nicode.net/#kqmoefix how the enable them.

Do you play in 3Dfx mode (which Glide wrapper and version)?

Did you try to run it in Software mode?
(disable 3Dfx/Glide in kqmoefix or edit the options.cs)

I managed to solve this problem. It was a setting you mentioned in KQ8fix that I had missed.

Unfortunately the game is much to sluggish to be playable.
Strange that something that can run Skyrim SE in without much stuttering can't handle such an old game.

AFAIK the GOG release includes an older version of nGlide.
A) disable Dynamic Lighting in the Graphics options
B) or install the current version of nGlide (and rename/remove the glide2x.dll in the game folder)
C) or try dgVoodoo

Thanks, I'll try your suggestion.
Edit: I'll try DG glide first since I have it already.

Edit 2: Neither made any difference.
Even the mouse pointer in the menu is so slow that it is just jumping around with little controll.