I ran...

apt update
apt list --upgradable

21 packages including...
xserver-common/stable-security 2:21.1.7-3+deb12u10devuan1 all [upgradable from: 2:21.1.7-3+deb12u9devuan1]
xserver-xorg-core/stable-security 2:21.1.7-3+deb12u10devuan1 amd64 [upgradable from: 2:21.1.7-3+deb12u9devuan1]
xserver-xorg-legacy/stable-security 2:21.1.7-3+deb12u10devuan1 amd64 [upgradable from: 2:21.1.7-3+deb12u9devuan1]

Then I ran...
apt full-upgrade
apt --purge autoremove

After that I logged out of X, and for good luck hit {CTRL}{ALT}{DEL}.
After the reboot, it all works properly. Maybe the crash to text
console caused the problem, and reboot alone would've been sufficient.
I don't know, but "all's well that end well".

--
Walter Dnes <waltdnes@???>
There are 2 types of people in this world
1) Those who can extrapolate from incomplete data