Backup locally or on a NAS, don't worry about losing the keys and all of your backups.

I'm using duplicity because none of these can sync to a rsync server that I run on my NAS.

You listed the main reasons, thanks.

As for remote backups - I use ssh with Borg and it works fine. If this is a NAS you can probably enable ssh (if it is not enabled already).

BTW for my remote backups I do encrypt them but this is a choice the author of Borg left open.

There are other issues with Borg such the use of local timestamps (naive date format, no timezone) instead of a full ISO8601 string, and the lack of capacity to ask whether a backup is completed (which is a nightmare for monitoring) because the registry is locked during a backup and you cannot query it.