Thanks for the report, @keithskim!
If you run this command in the terminal on “Mac #2” and “Mac #3”, is Mac 3 the only one where you see ‘rosetta not installed’?
/usr/bin/pgrep -q oahd && echo 'rosetta installed' || echo 'rosetta not installed'
If so, you will need to install Rosetta on that Mac to use backups at the moment:
softwareupdate --install-rosetta --agree-to-terms
(From your logs it looks like restic, the binary Local uses for backups, is not Apple Silicon native yet — that’s what the “Bad CPU type in executable” message at the end of the logs means. I’ll file a ticket with our team to look into this.)