I just updated to V8 as well on two machines (manual update from the LibreELEC menu). The first one (Intel NUC) looped during migrating databases. After deleting the Addons27.db and power off/power on it finally booted, but the system says my libraries are empty (I am using a mySQL database for several machines). I see my sources and contents, but obviously there isn't any connect to the SQL DB any more.
The second upgrade fulfilled without any loop, but the same result. All libraries are empty. How can I re-connect to the SQL DB?
For me the solution was "Wait for nerwork" (30 sec).