Backup client available on Internet without server NAT

Going through the documentation I understood that the server could connect to client instead of the contrary.
My goal is the following :
I have a dedicated server available and reachable on Internet.
I have a NAS running Debian at home (behind a provider box)
Is it possible to setup the server to connect to the client waiting for a connection instead of adding a NAT rule on my box to route outside port 55415 to my server.
I’m not comfortable to open port on Internet at home. I would like my personal network to remain personal.
Is it possible to run such a set up ?
Because so far the only way I had it to work was using NAT rule on my box so the client can reach the server on the TCP 55415.

Thank you very much for such a nice tool and your help.

No one knows ?
I just want to have a setup confirmation.