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I just rsync the root partition from time to time, ignoring /efi and /etc/fstab. Although this (obviously) only works in one direction, but that's enough for my use case.

Syncthing has worked fairly well for this. It has some caveats, and I don't recommend syncing anything other than some specific directories in your home folder to avoid conflicts with syncing config and cache folders.

What I synced: ~/files (contains all my projects, cat pictures etc.) ~/ide (contains just the IDE installation and other apps) ~/.ssh

Absolutely, +1 for Syncthing. I use it for pretty much all of my devices at this point, and it's maybe failed me... once over nearly 12 months of daily usage? For not having a centralized sync server, it works so much better than it has any right to.

Not OP but -

wireguard to git host of choice

git-annex is an awesome thing and much more useable then any of the normal sync services across the board (once you understand what it can do).

ansible to make all the hosts consistent configuration wise

I don't, but the things that I do are modular enough that I can make parts separately and plug them in when I come back.