Regarding Linux, WebDAV has been partially working/broken in Dolphin/kio since Plasma 5 on KDE. I've found the davfs2 FUSE module to be more reliable.
Sibling comment mentioned rclone, which is enabling piece of software and much better at webdaw than davfs2
I just imagined implementing webdav as a kernel module and I think I just broke my brain
Sibling comment mentioned rclone, which is enabling piece of software and much better at webdaw than davfs2