The Time Machine over NAS situation is very frustrating.
It used to be over Apple's proprietary AFP protocol. With the exception of Apple's now-discontinued Time Capsule product line, all NAS implement AFP using the open-source Netatalk, presumably with reverse-engineered AFP protocol. And it's unreliable.
With recent versions of macOS, Time Machine switches to SMB protocol. Apple has a custom SMB implementation, and all NAS use Samba. And it's still unreliable!
I guess the only reliable solution to use Time Machine over network is to use a Mac with File Sharing over SMB enabled. At least both ends run Apple's SMB implementation.
It used to be over Apple's proprietary AFP protocol. With the exception of Apple's now-discontinued Time Capsule product line, all NAS implement AFP using the open-source Netatalk, presumably with reverse-engineered AFP protocol. And it's unreliable.
With recent versions of macOS, Time Machine switches to SMB protocol. Apple has a custom SMB implementation, and all NAS use Samba. And it's still unreliable!
I guess the only reliable solution to use Time Machine over network is to use a Mac with File Sharing over SMB enabled. At least both ends run Apple's SMB implementation.