Actually, I think I solved it.
I don't know how this happened, but I looked at my outbound NAT rules under Firewall -> NAT -> Outbound.
There was only one rule here, from source any to destination *.
The issue? It was assigned to the "WireGuard Group". Presumably this worked in the past because I only had the one WireGuard interface, but once I added a second wireguard interface, this group now automatically included all WireGuard interfaces, so this outbound NAT rule now applied to all wireguard interfaces.
The second wireguard interface I was using to connect my phone to my LAN does not need (and probably should not have) outbound NAT rules, so I changed the interface for this rule from the WireGuard Group to applying only to the network associated with WG0 and now I can enable WG1 without it hosing wg0.
I hope this helps someone else. I have wasted hours troubleshooting this.
I'm not sure how it happened, if it was some weird default setting, or if I accidentally created it through some sort of typo during my initial wireguard setup, but at least now it is resolved.
I don't know how this happened, but I looked at my outbound NAT rules under Firewall -> NAT -> Outbound.
There was only one rule here, from source any to destination *.
The issue? It was assigned to the "WireGuard Group". Presumably this worked in the past because I only had the one WireGuard interface, but once I added a second wireguard interface, this group now automatically included all WireGuard interfaces, so this outbound NAT rule now applied to all wireguard interfaces.
The second wireguard interface I was using to connect my phone to my LAN does not need (and probably should not have) outbound NAT rules, so I changed the interface for this rule from the WireGuard Group to applying only to the network associated with WG0 and now I can enable WG1 without it hosing wg0.
I hope this helps someone else. I have wasted hours troubleshooting this.
I'm not sure how it happened, if it was some weird default setting, or if I accidentally created it through some sort of typo during my initial wireguard setup, but at least now it is resolved.
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