I recently upgraded from 21.04 to 21.10, the upgrade went fine, no errors or anything but now Ubuntu is shutting down randomly. Not crashing either though. The shut down prompt comes up randomly with options to shut down now or cancel with the 60 second countdown thing as if I had told it to shut down but even when I hit cancel immediately, the computer shuts off.
(This is on a System 76 Lemur that did not have this problem prior to the upgrade.)
Sorry, I'm a bit scant on the details, I'm not sure what would even be relevant because I have no idea what could even cause it to bring up the shut down dialog and then just shut off no matter what?
Editing to add the relevant section from /var/log/syslog as requested. Sorry it took so long to add. Earlier today it shut itself off twice within 20 minutes of each other but, of course, as soon as I was waiting to find an exact time for it to check the log as I didn't remember the exact previous time, it takes 2+ hours to shut itself off again.
Anyway here is the syslog for the last time it shut down, this is the whole exact minute so I hope whatever is causing the problem is in there. I looked at what it was but this is beyond me.
Nov 7 22:02:10 mildred systemd[1]: fwupd.service: Deactivated successfully.
Nov 7 22:02:51 mildred NetworkManager[3396]: <info> [1636340571.9197] manager: NetworkManager state is now CONNECTED_SIT
Nov 7 22:02:51 mildred dbus-daemon[3395]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' unit='dbus-org.freedesktop.nm-dispatcher.service' requested by ':1.7' (uid=0 pid=3396 comm="/usr/sbin/NetworkManager --no-daemon " label="unconfined")
Nov 7 22:02:51 mildred telegram-deskto[5110]: GDBus.Error:org.freedesktop.portal.Error.NotAllowed: This call is not available inside the sandbox
Nov 7 22:02:51 mildred systemd[1]: Starting Network Manager Script Dispatcher Service...
Nov 7 22:02:51 mildred systemd[1]: Starting Laptop Mode Tools - Battery Polling Service...
Nov 7 22:02:51 mildred systemd[1]: lmt-poll.service: Deactivated successfully.
Nov 7 22:02:51 mildred sh[10132]: laptop-mode: Battery polling disabled
Nov 7 22:02:51 mildred systemd[1]: Finished Laptop Mode Tools - Battery Polling Service.
Nov 7 22:02:51 mildred dbus-daemon[3395]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
Nov 7 22:02:51 mildred systemd[1]: Started Network Manager Script Dispatcher Service.
Nov 7 22:02:51 mildred whoopsie[4648]: [22:02:51] Cannot reach: https://daisy.ubuntu.com
Nov 7 22:02:51 mildred whoopsie[4648]: [22:02:51] offline
Nov 7 22:02:51 mildred NetworkManager[3396]: <info> [1636340571.9972] manager: NetworkManager state is now CONNECTED_GLOBAL
Nov 7 22:02:52 mildred telegram-deskto[5110]: GDBus.Error:org.freedesktop.portal.Error.NotAllowed: This call is not available inside the sandbox
Nov 7 22:02:52 mildred whoopsie[4648]: [22:02:52] Cannot reach: https://daisy.ubuntu.com
Nov 7 22:02:52 mildred whoopsie[4648]: [22:02:52] The default IPv4 route is: /org/freedesktop/NetworkManager/ActiveConnection/1
Nov 7 22:02:52 mildred whoopsie[4648]: [22:02:52] Not a paid data plan: /org/freedesktop/NetworkManager/ActiveConnection/1
Nov 7 22:02:52 mildred whoopsie[4648]: [22:02:52] Found usable
connection: /org/freedesktop/NetworkManager/ActiveConnection/1
Nov 7 22:02:52 mildred telegram-deskto[5110]: GDBus.Error:org.freedesktop.portal.Error.NotAllowed: This call is not available inside the sandbox
Nov 7 22:02:52 mildred whoopsie[4648]: [22:02:52] online