our team decided to make them mutually exclusive, therefore, at this moment you will not be able to utilize the Killswitch feature and have access to your LAN
Yeah, I got the same reason when I asked about that issue with Android (GrapheneOS). I didn't run into this issue on Windows. I don't recall Mullvad running into this issue, either.
ProtonVPN has also been the only known app impacting GrapheneOS shipping a DNS leak fix due to "Proton is doing something weird" that other apps aren't doing. Proton is also convinced they're programing their app correct and aren't open to fixing it....whereas Mullvad did when prompted.
Lastly...if the Killswitch and LAN access are mutually exclusive, why does Proton let me turn both on and not explain it? You'd think if you turned on the Killswitch, it would grey out the LAN access with a note saying you can't have both. And if you try to turn on the LAN access with Killswitch on? It should pop up with a notification saying you can't have both with a yes/no prompt to take you to the Killswitch settings to turn that off if desired.