The game freezes up on the initial loading screen for me, but it does it when it hits 100%. I can sit there for anywhere from 3-13 (longest has been 13 minutes, shortest has been 3 minutes. Usually it's anywhere from 5-7 minutes) before it responds and finally gets to the main menu screen.
The only way around this is I have to disable the game overlay function of Steam (if Steam is active) or the game overlay function for GoG Galaxy (if Galaxy is active). I always have both running and it doesn't matter if I launch my copy of BG3 off of Galaxy (which is where I purchased it through, GoG) or from the LariLauncher.exe as long as I have Galaxy open with the game overlay function active.
Once I disable the game overlay for both Steam and Galaxy, the game loads up in about 20-25 seconds.
Your issue sounds similar, so it might be worth trying to disable the game overlay option on Steam (and for GoG Galaxy if you have that running, too).
On a side note - I had the game crash on me a couple of times while running it in Vulcan, since then I've always ran it in DX11 and I haven't had the game crash since.
