It works for me on Fedora 34 as well as it worked before:
https://discussion.fedoraproject.org/t/how-ready-is-fedora-to-be-run-with-ipv6-only/61350/2?u=vgaetera
You can start troubleshooting by capturing the relevant traffic:
sudo killall tcpdump
sudo tcpdump -evni any udp port 547 &
sudo nmcli connection up id CON_NAME