I've just upgraded to 22.04.1 (from 20.04) and the Plank dock is no longer autostarting when I log in.
If I run a ps -f then I can see the process running, but there is no dock displayed.
If I kill -15 the running process and start it again from the terminal (no arguments, just plank) the dock appears and it is as it was before the upgrade.
I've checked dmesg for errors and can't see any mention of Plank in there.
I've also removed it from Startup Applications and re-added it.. still not auto starting, though.
(I've also checked under the settings menu on the login screen to see if I can reselect XOrg rather than the new Waylandengine but the only options I have are Budgie Desktop and Ubuntu.)
Using loginctl show-session $(awk '/tty/ {print $1}' <(loginctl)) -p Type | awk -F= '{print $2}' returns X11showing that I am already running XOrg anyway...
(As a side note, I also tried forcing XOrg via /etc/gdm3/custom.conf and uncommenting the WaylandEnabled=falseline.. but as I say, I was already running under XOrg.)