Hello @jschwart,
you can update your OVPN server with this (let’s assume you have the fd7a:2bc0:b1dc::/48 block configured in your router):
Take one /64 subnet from the ULA block that will be used as an address pool for client distribution (for example fd7a:2bc0:b1dc:cafe::/64).
Log in the router through the SSH.
Type in
uci set openvpn.server_turris.server_ipv6='fd7a:2bc0:b1dc:cafe::/64'
uci add_list openvpn.server_turris.push='route-ipv6 fd7a:2bc0:b1dc::/48'
uci commit
service openvpn restart
Try to reconnect with the OpenVPN client and you should have the ULA IPv6 addresses assigned on your tunnel interface and be able to ping other devices on your network.