SFTP with RSA generated key doesn't work

[gbrault]

1/ Have an SFTP server protected with an RSA Public key and use one generated with NextCloud (using Google Compute Engine can do the job)
2/ Get the private key from Nextcloud (and the paraphrase) and use it on the Nextcloud machine with an sftp CLI and make it work (I did it and will explain how)
3/ Try now to connect with NextCloud => it fails

So, their is an issue, namely Nextcloud is not able to pass the log in phase.

It's what we get in the log

Please find attached the file providing insights
sftp RSA bug.txt

[gbrault]

Forgetit! it work... made a trivial error!!!