Hi there.
I bought and tried Lethis a few months back. On my laptop with Intel HD 3000 graphics the map was not rendered. I tried it on another laptop with Intel HD 3000 and Nvidia (optimus) where it worked. I also found some information that indicated it needs at least OpenGL 3.2, which the Intel HD 3000 can not provide.

Well, I got a new machine with a AMD RX 560 which is capable of OpenGL 4.5. Same bug, the map is not rendered.

I can see some error messages, mostly GL_INVALID_ENUM in a number of files, among them TextureManager.cpp:412.
I also get GL_INVALID_OPERATION in MapRenderer.cpp:149 and TransitionRenderer.cpp:144. Those are likely the culprits. I can't debug it any further without access to the source.

Judging by the general quality of the game my guess is that this is not a wine issue but quite simply bugs. Windows users have crashes for what looks like similar reasons.

In Wine have you enabled core profile via MaxVersionGL? The one report also had some winetricks, but they didn't "know if that was needed or not".

Your posts lack basics such as system info, Wine version & build used, etc. You can try posting in the current Wine thread. Matruchus, or others, may be more likely to see it there. Probably should include what you have already tried. Speaking of which how about setting GLSL to disabled? Try with/without CSMT.

Any news regarding the current status of the problem?

The game is nicely discounted at the moment, but I'm not sure if I should purchase it or remove it from my wishlist...

Does it work under wine? Anyone?