I believe this is a OS specific bug. I am using custom sync server. Same settings works fine on Linux app, while it doesn’t work on both MacOS and iOS apps. If I clone the repo and run built/run bash script (dev mode), synchronization works (meaning can login to remote custom sync server).
Issue seems to be related to url parsing. When I use bundled MacOS app or iOS app I get the same error “error sending request for url ()”. And naturally there is no request reach to the server. I guess need to wait for the next release to be able to use the apps.