It is easy to get confused by multiple SSH keys formats. This handbook is to remind how any of the SSH key formats look like (what headers/footers are used) and how to run ssh-keygen
command to get expected result.
All the following examples are relevant for RSA key type and the following OpenSSH version:
$ ssh -V
OpenSSH_8.8p1, OpenSSL 3.0.5 5 Jul 2022