Migrated everything from the old MacBook Pro 2012 (that was starting to do weird things) to a 2019 model.

Told Time Machine (TM), yes, DO inherit the old backup. (Would have thought Migration assistant would take care of that.)

However, TM instead created a new backup set, meaning that (1) first backup takes ten to twenty hours; (2) identical files are being re-copied instead of hard-linked, doubling the space.

Subsequent backups are also taking longer than twelve hours—maybe due to free space being limited?

Finally, contrary to both documentation and experience from several years ago, neither backup set has the name of the computer it came from.

man page for tmutil and another post suggest the solution is either associatedisk or inheritbackup or both in unspecified order. But man page is unclear and what seemed to be the right arguments got error messages for both. Perhaps it needs to be different due to the fact that / and /System/Volumes/Data are now separate directories in the backup.

Anyone have successfully fixed such an issue on Catalina or Big Sur? (My Big Sur update is already in progress.)

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