Wireguard IPv6 doesn't work on iOS client, works on Windows client

[cinergi]

Hello,

I set up a Wireguard "road warrior" server configuration on my Opnsense box a while ago using the guide at https://docs.opnsense.org/manual/how-tos/wireguard-client.html.  It works fine using IPv4.  Recently, I added IPv6 and changed my client configurations accordingly to assign IPv6 GUAs.  My iOS clients do not have any IPv6 connectivity, but my Windows clients do using the same Wireguard configuration.  For example, if I go to test-ipv6.com from a Windows client connected via the VPN, I can see the configured IPv6 GUA address.  However, if I do the same from an iOS client, that test site reports no IPv6 connectivity.

I suspect this is a peculiarity of the iOS Wireguard client; has anyone else had similar issues?

Thanks!