Carbon Copy Cloner has a mode to periodically check backup integrity, and will alert you on mismatch. Given that unlike ZFS, APFS doesn't actually checksum user

Carbon Copy Cloner has a mode to periodically check backup integrity, and will alert you on mismatch. Given that unlike ZFS, APFS doesn't actually checksum user data, it's worth it for that feature alone. If you use ZFS for your backup destination, then this effectively ends up giving you verification of your non-ZFS source as well. And even if you don't backup to ZFS, then you still get notified that corruption was detected, allowing you to triage and take action. I think it's CCC5 or CCC6 that actually exposed the list of file mismatches to the user UI, but the diffs were greppable in the diagnostic logs all the way back to CCC3.