I've finally settled on Duplicacy. I've tried several CLI tools, messed with and love rclone, tried the other GUI backup tools, circled back to Duplicacy.
I run a weekly app data backup of my unRAID docker containers, which is stored on an external SSD attacked via USB to the server. The day after that runs duplicacy does a backup of that folder to Backblaze B2. My Immich library is backed up nightly and also sent to B2 via Duplicacy. Currently, those are the only bits of critical data on the server. I will add more as I finalize a client backup for the Win10, Linux, and MacOS devices at home, but it will follow this trend.