Files webDav webDisk support

I don't think the Files app supports webDav. You may be able to install a 3rd party app that supports webDav and includes an extension that Files could use. I haven't used webDav for a long time so I can't recommend any apps.

WebDAV access is less than fully documented, and there are published gaps in the support:

...If you use WebDAV to manage Pages, Numbers, or Keynote documents on iPhone, iPad, or iPod touch - Apple Support

SMB would likely be preferable, given the choice.