I was not sure, so I just performed the procedure again and even gave Roon as fresh an new install on my MacBook and used a USB stick for database migration to avoid any network issues
and YES, this time I can say for sure that I restored the backup successful before logging into my account.
What has improved? Roon now correctly displays “recent records”.
What did not improve? Roon is “circling” and “adding” and indexing for hours now and probably still some hours to come and I absolutely don’t get why that is.