It seems to work with the GOG installers on 24.0.5, as long as the graphics settings (quality, anti-aliasing and anisotropic filtering) are set to medium.
1) install HOMM V with Hammers of Fate into a new bottle by selecting the game from the presets (and replacing the steam installer with the GOG one,
2) install Tribes of the East into the same bottle by e.g. right-clicking on the bottle and then selecting Install Software into ...
One (or more) of the three settings mentioned above result in crashing, when loading the world map, but otherwise it stutters a bit from time to time, but not even close to being nearly as bad as it used to before.
It's actually playable!! Yay!
Gotta revise this a bit: it's playable in hotseat multiplayer (which is my usecase). Campaign crashes.