OVPN v6

Hi.
I have a OpenVPN server configured on CCR1016-12S-1S+ using IPv4. Some clients can not connect to the OVPN server because they have a IPv6 address.
I understand that IPv6 is not backwards compatible and I con not easily access IPv4 OVPN server from a IPv6 network.
What would be the best practice to solve this problem?
Can I use a 6to4 interface?

You can, but it won’t help you. OVPN server in current RouterOS doesn’t listen on IPv6.