I don't know if it's a smart solution but I have a HDD in my server that is used just for backups, each night I have rsync automatically moving stuff from multiple locations that I want to back up onto the drive. After that is done I have Kopia backup to B2, with compression, deduplication and encryption. I use healthchecks.io as well to alert me if any of the steps fails to complete (but none of the steps block each other).
Are firefly and actual different enough to justify running both? I'm looking into them myself.
As for suggestions on other things to host, maybe a recipe manager like Mealie, Tandoor or nextcloud cookbook?