The synchronization between different devices with the Synology with WebDAV no longer works. Separating and re-creating it does not solve either. In addition, the sync file was deleted on the WebDAV. I had problems with WebDAV before and it was difficult to set up. What other synchronization methods are there, not via a cloud service? How to set up a shared folder on Android iPhone and Mac? Fighting this problem again is really tedious so the application is not trustworthy.