On Wed, Mar 24, 2021 at 09:48:46AM -0500, Bob Tracy wrote:

(...) 
Everything worked as well as it's going to for kernel versions up
through v5.10.0.  When I boot on v5.11.0, "lightdm" starts, the screen
goes blank as usual, I get a mouse pointer as usual, and shortly after
that, the system locks up solid (completely nonresponsive except for
being able to ping it -- can't login remotely).  Recovery is via the
reset switch at that point :-(.
(...)

Same results for 5.12.0-rc4 kernel.

--Bob