I use MinIO as a backend for restic and autorestic. I target both a Backblaze B2 bucket, and a locally-hosted MinIO bucket. Works quite well, although I sometimes run into issues where the bucket is locked and restic craps out until I go run restic unlock manually. Some monitoring there is a good idea, if you go that route.
MinIO recently had some controversy and removed some nice admin UI features. Since you mentioned in your post you like TrueNAS because of a “user-friendly web interface” you would be stuck using the mc command (or buying a commercial license with MinIO to access some other web GUI they have for administration).
Since it’s photos you’re backing up, I’ll mention Immich which is self-hosted and you could setup to run on a separate system.
As an iPhone user, I personally use icloud_photos_downloader to grab photos from iCloud, store on ZFS, and shuffle off to B2 and MinIO via restic.
I run a second box with Proxmox Backup Server and I agree it’s a nice safety net for VM backup and restoring is dead simple. (Although that’s just the VM, underlying datasets that I mount as Samba shares in the VM aren’t backed up to PBS.). Highly recommend using PBS if you’re in the Proxmox ecosystem.