Back in the old Forum there was a thread on WebDAV clients that can be used independently of any file manager. Such a client’s main advantage over file manager specific handling would be its usability with arbitrary applications, eg. one could have their camera upload photos directly by pointing it there, or use a gallery without explicit WebDAV support. It should be usable with arbitrary file servers that reasonably implement the WebDAV protocol.
Back then, the conclusion seemed to be that OwnCloud could be used even with non-OwnCloud servers. I’ve tried reproducing such a setup with current NextCloud dev app, and while some results could be achieved by providing static status.php, index.php/login/flow and ocs/v1.php/cloud/user files, up to the point where SAF could be used to create collections on the server, and where images on the server could be viewed. But the overall experience indicates that this is clearly far out of spec for the NextCloud app. (Experience with OwnCloud was similar, just that I didn’ find a reasonablyowkring example for its ocs/v2.php/cloud/user file to begin with.)
Is there any app these days that provides a generic WebDAV SAF client, either one that’s already included in F-Droid (and just not advertised well) or that can be made suitable in cooperation with its author?