LGA1150:

I use ip6tables MARK and iproute2 rule to forward certain traffic to a WireGuard VPN interface.
When software flow offloading is on, IPv6 traffic over VPN no longer works, but IPv4 works fine.
A tcpdump check shows that offloaded IPv6 packets are routed by the main routing table instead of the one specified in ip -6 rule.

Both 5.4 and 5.10 kernel version have this issue.