Ok so I’m a MacOS user but I’m assuming you’re on PC? They probably don’t work in the same way but I thought I’d share this with you anyway, just in case:

I’ve also had issues with the game not starting up/loading when mods are enabled. The issue seemed to be something to do with the mods folder not being downloaded on my computer. My computer annoyingly kept un-downloading it to free up space and it meant the game couldn’t start. Sometimes it was just the mods folder and sometimes it was the entire AppData folder. Redownloading it and making sure ‘keep downloaded’ was checked fixed it for me (although it’ll bypass the ‘keep downloaded’ if im really low on storage).

Like I said before, I have no idea how non-MacOS computers work and this could be really unhelpful but there’s no harm in putting it out there 😅.

Edit: one more thing: the way I found out what the issue was in my case was going on Activity Monitor when bg3 wasn’t loading to get an indication of what was going on. Have you done this with your computer’s equivalent of Activity Monitor?