AVM tries to convince you to use their MyFritz service or another dyndns provider to use the new Wireguard
VPN which the new Fritzbox software supports.
Since I have a static IP and my own domain pointed to it, I have one of the use cases where a dyndns should not
be required. Perform the following workaround to enable Wireguard:
Go to the Dyndns settings and activate the use the following settings:
Use DynDNS: checked
url: http://httpstat.us/200
domain: yourdomain
username: xyz
password: 123
Your usename and password do not get sent to the httpstat server, but it simply sends a
OK back, so you can choose anything for username and password or leave it empty if FritzOS
supports that.
The domain must be either your domain or possibly this also works using the static IP address (try it out).
This field must be correct, since it is later used in either the displayed QR code or included in the Wireguard settings
file. Otherwise, connection from the client will not work.
Thanks to reddit user aMpeX for providing the httpstat part of the workaround, which I modified to not send any
data to the server.