I have a Time Machine sparsebundle backup on an NTFS volume on a USB drive. When I wanted to restore from it I connected it and the volume was mounted as read-only, but I was unable to mount the sparsebundle and migration assistant didn't offer it as a source to restore from.
After copying the sparsebundle to a read-write HFS+ volume (on a USB drive) I was offered the option to restore from it, leading to my question.
What are the requirements to be able to restore from a sparsebundle? Is it that the containing volume is writable, or something else?
Background
I'm doing my backups over SMB, so I want a file system that's journalled on Linux (i.e. I can't use HFS+) and from which I can restore when using it as a USB drive (so far not NTFS). I'm aware of paid drivers for NTFS on macOS, but I'm initially looking for a free solution for Mojave.
The ntfs-3g project seemed completely dead judging by its website, and the install/compile instructions seemed lacking and outdated (packages from 2015 as opposed to the latest release in 2017).