Can't get back to KDE Plasma session after selecting KDE Cinnamon session

[Steven Friedrich]

I selected Plasma at the sddm login screen, but it takes me into an 
obvious Cinnamon session, an error message in there proves. it:

Problems during Cinnamon startup...
Unfortunately, the notification dialog doesn't allow cut and paste.
-- 
Donald Knuth - I've proven it's correct, but I haven't actually tried it.

HP-Slimline 290-p0014 Desktop using integrated UHD Graphics 630

Running KDE Neon 5.21.2, Kubuntu 20.10, Linux Mint 20.1 Cinnamon, and

FreeBSD FreeBSD 12.2-RELEASE-p4 FreeBSD 12.2-RELEASE-p4 r369434 Special  amd64

Path: /usr/ports
Working Copy Root Path: /usr/ports
URL: https://svn.freebsd.org/ports/head
Relative URL: ^/head
Repository Root: https://svn.freebsd.org/ports
Repository UUID: 35697150-7ecd-e111-bb59-0022644237b5
Revision: 568188
Node Kind: directory
Schedule: normal
Last Changed Author: nc
Last Changed Rev: 568188
Last Changed Date: 2021-03-12 11:26:49 -0500 (Fri, 12 Mar 2021)