Full new release or not, I am not installing this until I know for certain it will not break our current environment (Serv-U 15.3.0.1375)

Same. I'm also waiting for some additional feedback from the forum before we install. I already entered a ticket for clarity on "Removal of DSA 2048 and 4096 SSH private keys" just to ensure that won't impact any partners using DSA keys connecting to us. I'm pretty sure it won't but better safe than sorry. 

When I remove the certs..  of course it's unsecured but it's working   as soon I put back the cert  key  it goes down ERR_SSL_VERSION_OR_CIPHER_MISMATCH

Got it working !

our .pem had info not needed.   clean it  and it's working

When you say clean it do you mean it had sections which are not required so just removed with a Text Editor? If so which section(s)?

So i have update on the weekend and got the same issue, did someone know the real workarround?

If you need to get back up and running, recreate your CSR and private key for the SSL certificate and it should resolve it. I've only seen it once and it appears to be to do with this, an old cert or key format and creating a new one resolved it. I would recommend you raise it with Solarwinds Support though as they may be able to tell you exactly what the issue is?

Just to clarify, you'll need to get the cert re-signed or issue a self-signed one once you create a new CSR and key, as the old cert wont match.

I would recommend to check whether the certificate size is bigger then 4kB. There is known issue with higher sizes. If this is your root cause, there is BuddyDrop you could receive through support.

Otherwise, reach to SWI support and provide appropriate info for investigation, if possible.

Upgrade of OpenSSL touched security settings of most parts of Serv-U.

There is high chance, that old certificate - especially signed with low encryption methods may not be accepted anymore.

Your way to get a new and secure certificate is one of the best options you could do.