OpenVPN gateway with OpenWrt in home LAN

[FunThomas]

Hello,
i have a Fritzbox and want to give to some devices access to a VPN over a raspberry pi 4b with OpenWrt installed in the same subnet in home LAN.

i have used the guide from

OpenVPN client using LuCI

with network killswitch enabled.

My problem is now with IPv4 only all is fine and if i set the devices DNS and Gateway to the IP of the OpenWrt my connection seems to be fine with ipleak.net and dnsleaktest.com but if i enable IPv4 + IPv6 on my device then it detects my real connection & location.
The Fritzbox has DHCP enabled and the OpenWrt too. so i don't know what ipv6 is used.
Is there an easy way to secure the devices that all traffic goes through the vpn besides disabling ipv6 on the devices?
i think i understand most things of ipv4 but ipv6 i'm lost with dns & masquerading & co
so help would be really apreciated

edit: it would be good if the devices still have access to the home LAN

best regards,
Thomas

[mk24]

Does your VPN service support IPv6? If it does not, you'll need to prevent devices from trying to use IPv6, as that will be a direct connection through the Fritzbox.

Other than completely shutting down v6 for everything in the LAN, it isn't going to work to have one network. The alternative is to put VPN users in a v4 only network on the other side of the Pi.