Xorg crashes on Raspberry Pi Ubuntu Mate

Support & Help Requests Raspberry Pi
#1

A fresh build of Ubuntu on Raspberry Pi, with MATE (downloaded using tasksel) will experience Xorg will crash reliably when "switch user" is selected from the menus.

So, login and then go to switch user. Hiccup and then pause but nothing too terrible on the UI. Crash file generated. Every time.

Sample crash file here: http://www.button.network/_usr_lib_xorg_Xorg.0.211018a.txt

CLUE #A

If I log out, instead of switch user, and then log in under the new ID, no crash file is generated.

CLUE #B

The crashes happen if config.txt looks like this:

# Place "config.txt" changes (dtparam, dtoverlay, disable_overscan, etc.) in
# this file. Please refer to the README file for a description of the various
# configuration files on the boot partition.
dtoverlay=dwc2,dr_mode=host
dtoverlay=vc4-fkms-v3d
disable_overscan=1

But they don't happen if config.txt looks like this.

# Place "config.txt" changes (dtparam, dtoverlay, disable_overscan, etc.) in
# this file. Please refer to the README file for a description of the various
# configuration files on the boot partition.
dtoverlay=dwc2,dr_mode=host
#dtoverlay=vc4-fkms-v3d
#disable_overscan=1

The line dtoverlay=vc4-fkms-v3d was needed to get the video display to look OK. Without it, the screen has black bars on the top and the side. So, currently I have a choice between crashes and black bars.

#2

Did I post this in the wrong place? Say something wrong? Or am I hanging out on the edge with a mix of technologies where no one is expert?

#3

I expect it's simply that very few people will bother with multiple user accounts at all on something like a Pi, let alone running them concurrently.
(I did actually set mine up that way, but haven't ever had more than one active at a time).

The bug is likely around getting DRI leases, but that's just the best guess I can come up with.

add> Your setup actually does better than mine: if I try to switch user, all that happens is a change to a new VT (with a cursor visible at top left) for a few seconds, then it falls over and takes me back to the lightdm screen.

So, I can confirm something's broken in there, but can't help you, sorry.

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