FTPS (TLS) stopped working

Hi, after last system update, FTPS has stopped working. I can connect thru FTP but not FTP-SSL (Explicit AUTH TLS). This worked fine before on Cyberduck, Filezilla & others.

I've made sure FTP PASV Mode is On, disabled Firewall, restarted in Safe Mode and removed certificates from Keychain Access to no avail.

Same connection on a Windows 10 & Linux guest OS on VirtualBox work as expected, as well as on other Windows computers. I don't have another Mac to try it, but I've been talking to my Host Provider and it seems clear it's a Mac problem.

Any suggestions?

Thanks truly.