I use my Nextcloud install (since it provides a WebDAV interface). In the options under the Sync tab, I select WebDAV as the File Syncing type and for the URL

I use my Nextcloud install (since it provides a WebDAV interface). In the options under the Sync tab, I select WebDAV as the File Syncing type and for the URL I put: my.nextcloud.server.com/remote.php/webdav with the appropriate credentials. Works flawlessly.