In the past, I've heard recommendations not to use remote Time Machine over SMB directly, but rather to create an APFS disk image on a remote server and then backup to that as if its an external hard drive.

Supposedly, doing that eliminates a lot of the flakiness specific to SMB Time Machine, and while I haven't tested it personally, I have used disk images over SMB on macOS Tahoe recently, and they actually work great (other than the normal underlying annoyances of SMB that everyone with a NAS is mostly used to at this point).

The new ASIF format for disk images added in Tahoe actually works very well for this sort of thing, and gives you the benefits of sparse bundle disk images without requiring specific support for them on the underlying file system.[1][2] As long as you're on a file system that supports sparse files (I think pretty much every currently used file system except FAT32, exFAT, and very old implementations of HFS+), you get almost native performance out of the disk image now. (Although, again, that's just fixing the disk image overhead, you still have to work around the usual SMB weirdness unless you can get another remote file system protocol working.)

[1]: https://eclecticlight.co/2025/06/12/macos-tahoe-brings-a-new...

[2]: https://eclecticlight.co/2025/09/17/should-you-use-tahoes-ne...