ipv6 vs. ipv4

[Hendrik Friedel]

Hello,

I understood that wireguard prefers ipv6 over ipv4 by default.
Nevertheless, on both Windows and Android I do not get a connection 
(only sent bytes no received bytes) when using my domain 
(friedel.dynv6.net). If I use the IP 
(2a00:6020:1bfb:c700:ba27:ebff:fe3e:6c55), I get a normal connection.
I can imagine that WG uses ipv4 (the A-record is set, I cannot change 
that, but it points to an invalid ip)

How can I -when using the domain- enforce that ipv6 is really used?

Apart from that, my suspicion is that ipv4 is in fact used here... How 
can I really find out, why I get no bytes on the received counter?

Best regards,
Hendrik