Go to the the games folder (it's called Bloodlines 2), delete the folder called "Launcher" and then you can start the game via ether the Bloodlines2.exe inside the main folder. Or with the executable inside sub-folder Bloodlines2/Binaries/ Win64. If you are afraid that Paradox will change this, download the offline install files via GoG Galaxy or the GoG website and you can install the current version any time you want. I will add my thoughts on the game itself game later. So far I dislike the Launcher situation, the enabled by default telemetry collection (although you can turn it off in the games settings) and the menu design which was clearly made with controller first in mind (which is fine on console but not on PC and reminds me of PC ports in the 2010s and not in a good way).
The Definitive Edition has it's flaws without a doubt, but the potential (especially for modders) is insane. The Engine upgrades alone making sure of that. As someone who has stopped playing DoW without Ultimate Apocalypse many years ago, I can't wait to see what the team behind UA will do with this. While yes, as of now (20.08.2025) there are problems with compatibility, they are actively working on it. Also, the Definitive Edition has gotten two updates since launch, so I'm very hopeful that at least most problems will be fixed. One thing I'm not sure about every coming back is local multiplayer, which is a shame at best (as if that will stop piracy, lol).
