NetworkManager’s Gnome GUI works with wireguard config files. If you are using Plasma you would need to install some alpha software to do that in the gui but you can always fall back to nmcli which also supports wireguard configs via the import command.
A while ago there was a prediction about the true intentions of the russia negotiating: they want to stop Ukraine from succeeding as a state, since that would be a bad omen for a neighbouring kleptocracy.
If this prediction comes true the outcome you describe is actually very unlikely, because the russia would rather continue fighting just to keep the region in shambles.