Also note that when you see a public key being added on bionic that is because I put it on /etc/cloud/cloud.cfg to be able to login since it cannot use the metadata service. Also on bionic clou-init is "Cloud-init v.18.5-45-g3554ffe8-0ubuntu1~18.04.1" and on xenial is "Cloud-init v.19.1-1-gbaa47854-0ubuntu1~16.04.1". The one on xenial is more recent.
Also note that when you see a public key being added on bionic that is because I put it on /etc/cloud/ cloud.cfg to be able to login since it cannot use the metadata service. Also on bionic clou-init is "Cloud-init v.18.5- 45-g3554ffe8- 0ubuntu1~ 18.04.1" and on xenial is "Cloud-init v.19.1- 1-gbaa47854- 0ubuntu1~ 16.04.1" . The one on xenial is more recent.
Orestes