I've been using Restic for a while, and it's backing up to a Hetzner storage box (1TB).
Restic supports encryption, compression, deduplication, and can forget old backups in a spread out timeline (configurable; e.g. save one yearly, three monthly and 7 daily).
On top of this I also use healthchecks.io to make sure all backups are working.
I've been wanting to switch to PhotoPrism for a while. Is face/object detection any good, compared to Google Photos? Do you need powerful specs, or can a low-spec machine handle it?
I self-host my own mail server. I don't send many emails, but they seem to be arriving correctly whenever I do at the moment, but it wasn't always like this. I've properly setup SPF, DKIM and DMARC, which helps a lot, but my IP address was blacklisted on some servers from a previous owner I guess. I have a VPS from OVH. I had to manually fill out some forms to get Microsoft Outlook to accept emails from my server. Despite that, it has been working flawlessly. I have my own domain since 2017, and I'd say the age of the domain is also important.
I'm in the process of migrating my servers to NixOS. It takes a lot of time and the learning curve is steep, but I have one config shared for all the servers and PCs. I have setup the servers to automatically pull the latest configuration everyday and even restart if there's a kernel update.
This means I just need to update my laptop and push the changes to the repository, and all the servers will also update.
I haven't had this setup long enough to know if things will break unexpectedly with updates tho. NixOS has a great feature where you can rollback to a previous configuration (generation) with a single command. You can always keep using containers to isolate updates, if you want (Nix allows you to declare those in the config as well).
As an example, you can take a look at my config.
EDIT: Systemd timers have an option to randomize the time a service runs, I use it all the time. The option for Nix's config pulling is using systemd timers, so you can use that.