Maintenance for the week of November 3:
• NA megaservers for maintenance – November 3, 4:00AM EST (9:00 UTC) - 12:00PM EST (17:00 UTC)
• EU megaservers for maintenance – November 3, 9:00 UTC (4:00AM EST) - 17:00 UTC (12:00PM EST)
• ESO Store and Account System for maintenance – November 3, 4:00AM EST (9:00 UTC) - 12:00PM EST (17:00 UTC)
• https://forums.elderscrollsonline.com/en/discussion/684716
Thank you from me, as well, as I just upgraded to Catalina and ran into this same issue. I was in "Windowed (Fullscreen)" mode, but switching to plain "Windowed" fixed it, and then I was able to switch back to "Windowed (Fullscreen)" again.
Edit: I exited and restarted the game as a test, and I get the white screen all over again when it starts in "Windowed (Fullscreen)," which is a pain; but at least now I know how to deal with it.