solved this bit. It did not work due to this problem. After dis-/enableing the lxd snap I can set the IP address.
however I am facing a connection problem with the remote IP now
lxc remote add hetzner [xx.yyy.zzz.xxx]
Generating a client certificate. This may take a minute...
Error: Get https://[xx.yyy.zzz.xxx]:8443: Unable to connect to: [xx.yyy.zzz.xxx]:8443