Upgrade Sonarqube LTS to 9.9 from 8.9 with expired license

Our developer license has expired and as the renewal takes some time to approve and etc.
we wanted to use the downtime for an upgrade of our Sonarqube 8,9 LTS to 9.9 LTS
and an upgrade the used PostgreSQL database.

Is it correct that an expired license only causes that analyze is paused until a valid license is installed ?
Is there any known issue of doing a Sonarqube upgrade from 8.9 LTS to 9.9 LTS, while there is no valid license installed ?

Yes, and no, respectively. Since you can’t test your upgrade afterwards, so I would suggest keeping a backup of your v8.9 database until you can test analyses on the new version.