Currently, mullvad selective routing is configured to connect to only one server, and it is working correctly.
I would like to add several more countries to the configuration.
However, because the tunnel address is identical, it seems that only a single instance is being utilized.
After adding peer settings for another country, it appears that routing is performed only through the newly configured country's server, rather than the server that was originally in use.
Mullvad allows a maximum of five devices.
Is it possible to use multiple country endpoints simultaneously while using the same WireGuard private key?
It's one peer per instance.
I don't think it's a WG limitation but rather just a fact of life when you're connecting to a public VPN. The clue is that each peer necessarily has "0.0.0.0/0" and "::/0" as the Allowed IPs in order to let you access the whole internet, which means they overlap and the routing is ambiguous.
You would need to policy route to separate gateways I think, and each one will cost you a device allocation on your account.
Cheapest clean way that isn't a hack: just manually switch the peer on your existing instance as needed.