While experimenting with ProtonVPN's Wireguard configs, I realized that my real IPv6 address was leaking while IPv4 was correctly going through the tunnel. How do I prevent this from happening?
I've already tried adding ::/0 to the AllowedIPs option and IPv6 is listed as disabled in the NetworkManager profile.
If you disable IPv6 at the kernel level there's no extra latency as nothing even tries to connect to an IPv6 address. It's a shame to have to do it, but does fix the issue.