samba/ ksmbd would probably be the closest equivalents; sftpd is always an alternative, somewhat easier to set up, but slower and (on the client side) often less integrated into commercial operating systems.
Perhaps I'm not conveying this idea clearly enough - I have a Mac and I want to use Time Machine built in the OS to do backups to an eSATA-connected disk on my router.
Would SAMBA be the preferred network protocol or Netatalk?
As for why we still need netatalk, it was only after 10.14 or so that MacOS supports TimeMachine over SMB shares.
We have a 10.13 Mac that can't have the OS upgraded further... and while we know we should put it out of its misery and probably has more vulnerabilities that anything else, it will stay there yet for a while.
We are currently using a D-Link NAS which is even older to backup it, which is completely maxed out from a RAM/CPU point of view, and that probably would be compromised if anyone even looked at it sideways.
I managed to build a netatalk_3.1-18-3 package, and it seems to work fine on an ipq806x. Needs a small patch for a weird error that I will investigate further. Besides that...
How do I bring this package back from the dead? What's the process for that?