I really thought about doing this. A Dell Optiplex has this feature in BIOS as far as I know.

So, it should be really simple from this point:

1. Run systemd timer at the time of the night where the remote machine should be started
2. Ping the machine on it’s wireguard interface until it answers
3. SSH into the machine and do some basic checks
4. Run backup script to do backup via borg to remote repository
5. Shutdown the remote machine

Optionally, keep a config file for the script on the local machine. For eample, I do not want to shutdown the machine after the backup one single time, to be able to do some updates of the remote machine the next morning and shutdown it by hand afterwards.

Wow, thanks. I wonder how I missed that.