Catastrophic failure, MQTT stopped working even after full restore and host reboot, completely stuck

Installation
1

Background: HA 2021.6.2, Rpi4. Had delay in zigbee/mqtt, some recommended installing Mosquitto 5.1. Couldn’t install that, reinstalled latest 6.0.1, now no mqtt devices work.

Tried: complete full restore of previous config, full host reboot, still not working. Zigbee2mqtt detects devices and actions such as button presses correctly. After the full restore, these also stopped working: history, recorder, logbook, automation. I can’t update nor restore (“system is starting” for 20 minutes now).

Here’s Supervisor log, Core log, Mosquitto log (nothing wrong), HA log.

I can’t restore or create snapshot, because

21-06-08 10:09:29 INFO (MainThread) [supervisor.jobs] 'SnapshotManager.do_snapshot_partial' blocked from execution, system is not running - CoreState.FREEZE

Please help, my home is almost useless without this. I’m completely stuck. Can’t update, can’t restore, can’t do anything. Thanks.

2

Apparently it took more than half an hour without any notice or notification to restore the snapshot. It booted while not being fully ready, spitted out a bunch of error messages about mqtt and THEN proceeded to - - apparently - continue the restore in the background. MariaDB database got corrupted, so I had to uninstall/reinstall.

I understand this is complicated stuff but the restore process needs some more UX care.