JohnW, thanks for this. It did not solve my problem directly, but definitely put me on the right trail.
First off, I was running an older version of Proton. So I brought it up to version 5. Secondly, Wine complained that it could not find the proper FreeType font library -- not a deal breaker. The interesting bit for me was that in the background, crashpad issued a "File not found error" and puked up a distinctly MS-esque error in a "DEVICE LOST" window stemming from Vulcan (unrecoverable Vulcan error). I finally got the game to launch by forcing the BG3 executable to evaluate an invalid argument (-x)
The invalid argument also gave the 'device lost error' but in addition noted the improper optional parameter and offered me the option of cancelling the launch of the game (which went ahead and launched in the background anyway). Cancelling out of those errors terminates the game. Leaving the error boxes up allows the game to continue to the opening screen.
Weird. I will have to find a better way to trace what is going on under the covers, but in the meantime I think I will see how far I can get the game to go.
Again, thank you for taking the time to post.