You can ssh to your router with ipv6 address
on your PC try
ip -6 route|grep via ssh -6 root@hex:hex:hex%enp0s31f6
It seems like dnsmasq isn’t running, usually that is case when it tries to listen on port 53 which is occupied with kresd/unbound.
Check on router
uci show dhcp.@dnsmasq[0].port=‘0’
or set it with command
uci set dhcp.@dnsmasq[0].port=‘0’
uci commit dhcp
/etc/init.d/dnsmasq restart