sarge33rd: Has anyone got it working with their GOG install? Please tell me precisely step by step, how you did.
Sorry for the late reply; Solasta worked out of the box on my initial install, but when I went to see about mods to answer your question, it naturally didn't work any more. I found and fixed the issue, and successfully installed this and other mods with no trouble. Telling you exactly what I did is pointless, since I use Linux/Wine. However, here's what I did:
1) Download and Install
Unity Mod Manager. It's best to get recent enough that Solasta is in the game menu. I installed the latest (0.23.4d). I already had it installed for use with Pathfinder: Kingmaker.
2) Download
the mod. I downloaded v1.1.0.
3) Run UnityModManager.exe (I used mono to run it under Linux, but you should be able to just run it directly under Windows). Select Solasta as the Game. Select the install folder under Folder (gog uses Solasta Crown of the Magister rather than just Solasta). Click Install (or Update if you have already done this step).
4) Go to the Mods tab and press "Install Mod". Select the mod's zip file. Or, I guess you can drag & drop the zip file into the drop area. The mod should then appear in the listing above, with status OK.
5) Start the game. The UMM GUI should pop up almost immediately; you can exit it (and redisplay it) w/ ctrl-F10. The mod should appear in the list and have a green light.
6) Test: start a new game and verify that it skips the intro tutorial. It did for me.