Windows 10 - Create automatically VPN IPv6 route

[vpnuser]

Hello,
following configuration: OPNSense as IPSec / IKEv2 VPN server with Windows 10 clients. At the moment I set the routes on the Windows client using the Powershell command Add-VpnConnectionRoute.
I read in this post https://wiki.strongswan.org/issues/817 that the IPv6 route can also be set automatically. Quote:

It turns out Windows (10) accepts unicast router advertisements directed at the virtual address of an IKEv2 interface, and doesn't need a link local address for this to work.

So, I just have an updown script like yours add the client's virtual IPv6 address to a clients{} block in /etc/radvd.conf, using stock (Ubuntu) strongSwan on the server.

I tried to make the appropriate entries (via shell) in radvd.conf. Unfortunately this does not work. Does anyone have experience with this and can help me with the entries for radvd.conf?