My home LAN is all on 192.168.0.0/24, with the actual LAN and the WireGuard LAN being on separate subnets. I also disabled the kill switch in WireGuard so that it wouldn't lock Mullvad out, but it still results in Mullvad's LAN taking complete precedence over WG and cutting me out of that back-to-home connection. Best part is trying to look up this problem online since Mullvad also uses WireGuard, and search engines don't differentiate if you're asking about the standalone client or the direct WG configuration from Mullvad.
Ideally I want Mullvad to always be on to act as an online condom with WG kicking in whenever I'm not connected to home WiFi, so that at home it's not doing any unnecessary routing and AFH it's giving me access to my home network, including the home DNS server with local domain names for my home lab.