I can confirm that wdfs has problems with nextcloud URLs, but I cross-checked it with GMX and it works fine there. Unfortunately I don't currently hav access to any other WebDAV ressources I could check it with. Given that wdfs itself has not changed for years, I'd suspect that the regression got caused or at least triggered by some recent change in nextcloud or in one of the libraries that are used by wdfs. This needs some thorough debugging, or maybe we should just drop wdfs because the upstream author abandoned it more than 10 years ago.