Is there a browser extension to do this automatically?

None of these work in Raccoon (Android client).

I’d rather not use a computer at all than use GNOME for the rest of my live.
For me it’s KDE Plasma all the way.

Proxmox is pretty much focused on ZFS, LXC containers and VMs. You want mergerFS and Docker. I say avoid Proxmox and go for Debian or another distro.

Only when using zfs, which op is not.

LUKS does offer multiple key slots. You can have the OS unlock it with a keyfile and be able to manually unlock it with a keyphrase when you don’t have access to that file.
I’m not sure if you can tell the OS to unlock it with a passphrase on boot like with the root partition.

You can always have a copy of the keyfile somewhere else, on an USB drive for example.
Alternative is to also add a passphrase to the /home luks partition.

I always wondered the same about ZeroTier. If the controller is under foreign control, isn’t the whole network compromised?

There are often some “fair use” paragraphs in their respective ToS that they could enforce and either terminate your account or request you to uprade to a higher tier product. Usually (not always) VPSs are overprovisioned, so when people start to fully utilize their rented machines theit whole business model goes belly-up.

Be careful with compute intensive tasks. Some providers don’t like when you actually utilize your rented hosts.

Without sudo? :D

Not exactly federated, but open source: https://github.com/Alovoa/alovoa

What am I seeing here exactly?

What you call an algorithm here is a recommendation engine. I don’t see why they should avoid having something like that. Ideally they would have a modular system, so you could plug in your own favorite third-party engine.