I had this issue (not able to connect to HA, version 5.9) which led me to re-install HA and restore from latest snapshot. It looks that same functionality is there after the restore but now I’m facing issue with Supervisor menu on the left side of the front page.
I noticed before restore that supervisor item had been removed but after the restore it is again there. When I click it and empty page opens and there is a spinning wheel in the middle. That is all I get, I have waited 10 minutes but it doesn’t advance anywhere from that.
I read somewhere that supervisor had been merged into Configuration. Maybe the backup containing old UI layout/menu settings is not accepted that well by the new HA version (8.2)…
Any advice how to fix this? As this is not working I do not know how to access my add-ons. I need to because Google drive snapshot backup add-on is complaining about some non-existing URL…