Really some “known or traceable” ID is required but Gitlab Enterprise tends to throw an unhelpful message. Fresh advice was given last week.
In case any other user can help with slot change advice please can you tell us if the Bootloader is locked.
If you wanted to experiment with recovering the situation would you consider removal of your Google account if only to establish if this is a part cause of your issue? No guarantee this would help, ofc.
Capture a debug information from /e/OS might ofc help.
Seedvault is available from Settings > System > Backup. You might find this helpful if you decided to go for Factory reset. It is not a fully comprehensive backup so please take notes as you proceed so that you are fully aware of what is not backed up.