Question Ubuntu 18.04.2 with OpenSSL 1.1.1 / TLS 1.3

[learning_curve]

SFTP is using SSH as it's transport protocol and the encryption is not based on SSL/TLS - thus it's not using TLS 1.2 or 1.3 and not affected by all of this.

Yes, that's 100% correct and is one of the main reasons we prefer it to FTP and only use SFTP now. It was actually the Plesk / Firewall issue that we were wondering about... because it seems that your issues began (we think) once you upgraded Filezilla to v3.40 and then used it whilst also using FTP / TLSv1.3 within Plesk. The curveball being, that SFTP can / will provide a good alternative option regardless of TLSv*** until the Filezilla FTP issue is solved.

We included the TLSv1.3 reference in the previous posts, because of any possible 'collateral damage' elsewhere (e.g. SFTP) caused by, either its own inclusion and/or the the required different OpenSSL that's needed and/or the new ciphers that are also needed etc as we currently don't run any of those but you do.

Our apologies because when reading back; where we said "...have you tried Filezilla SFTP using TLSv1.3 (within Plesk) instead of FTP yet?" We can see we didn't make our own question, but more importantly, its context, anywhere clear enough

 

[ChristophRo]

Another addendum regarding FTPS with Filezilla v3.40 and TLS 1.3 connections.

Same problem (transfer errors while uploading) happens when using vsftpd (v3.0.3) as FTP server.
According to the "Internet" similar behaviour is shown with the pure-ftpd server, though I did not test that myself.

Left we wondering if there is any FTP server out there, that works properly with TLS 1.3 and Filezilla Client v3.40....

 

[learning_curve]

....Left we wondering if there is any FTP server out there, that works properly with TLS 1.3 and Filezilla Client v3.40....

Come in FTP.... TLSv1.3 & Filezilla are in town, so your time appears to be up
SFTP... Get your gear ready, you're going to be busy