a freshly provisioned instance has additional files in /etc/ssh/userkeys, see below, also related to T81099
$ sudo find /etc/ssh/userkeys/ -ls 402078 4 drwx------ 4 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/ 402079 4 drwxr-xr-x 3 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/ubuntu 402080 4 drwxr-xr-x 3 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/ubuntu/.ssh 402082 4 drwxr-xr-x 3 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/ubuntu/.ssh/authorized_keys\ 402083 4 drwxr-xr-x 3 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/ubuntu/.ssh/authorized_keys\ /public 402084 4 drwxr-xr-x 3 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/ubuntu/.ssh/authorized_keys\ /public/keys 402086 4 drwxr-xr-x 3 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/ubuntu/.ssh/authorized_keys\ /public/keys/ubuntu 402087 4 drwx------ 2 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/ubuntu/.ssh/authorized_keys\ /public/keys/ubuntu/.ssh 402088 0 -rw------- 1 ubuntu ubuntu 0 Jan 5 17:05 /etc/ssh/userkeys/ubuntu/.ssh/authorized_keys\ /public/keys/ubuntu/.ssh/authorized_keys 520863 4 drwx------ 3 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/root 520864 4 drwx------ 3 root root 4096 Jan 5 17:07 /etc/ssh/userkeys/root/.ssh 520877 8 -rw------- 1 root root 4709 Jan 5 17:07 /etc/ssh/userkeys/root/.ssh/authorized_keys 520865 4 drwxr-xr-x 3 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/root/.ssh/authorized_keys\ 520866 4 drwxr-xr-x 3 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/root/.ssh/authorized_keys\ /public 520867 4 drwxr-xr-x 3 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/root/.ssh/authorized_keys\ /public/keys 520868 4 drwxr-xr-x 3 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/root/.ssh/authorized_keys\ /public/keys/root 520869 4 drwx------ 2 root root 4096 Jan 5 17:05 /etc/ssh/userkeys/root/.ssh/authorized_keys\ /public/keys/root/.ssh 520870 0 -rw------- 1 root root 0 Jan 5 17:05 /etc/ssh/userkeys/root/.ssh/authorized_keys\ /public/keys/root/.ssh/authorized_keys