Hi,
my further research showed me a lot of similar issues with corrupted sqlite database. To be honest, trying to fix it in the described way seems to be -at least with hass.io av OS- a hassle. Instead, I copied the backup files from my VM to an freshly installed HomeAssistant on a Debian11.
Then I restored the backups from the last full one (from May!) step-by-step all partial ones. Had some glitches in between as the GUI did not come up after one restore. So I had to do it with the ha backup restore command on CLI. But in the end it worked fine so far and I got a running instance with all my sensors back.
The history of my data got lost (at least in Influx/ Frafana) but this doe not bother me.
As I moved to Debian I am now able to create a cronjob for future daily backups and backup these through rsync to a remote location. Ways better!
/KNEBB