It does appear that you have addressing working but not connectivity. As I said, I’m no expert on OPNSense but I did find this thread which has some thoughts: forum.opnsense.org/index.php?topic=29459.msg14233…
In -> Firewall -> Settings -> Advanced. Make sure the checkbox “Allow IPv6” in enabled for obvious reasons.
As well as:
You just have to choose for hybrid Firewall: NAT: Outbound and add a rule to it:
Interface: WAN Protocol: IPv6 pass from any to any
This latter rule is… odd to me since there shouldn’t really be NAT for IPv6 to a delegated prefix. But maybe that rule is meant to effectively disable the NAT and allow traffic to pass straight through without translation, obviously after applying your firewall rules.