When I login to Spotify, it redirects to non-existing localhost page

You need to start the login process via in-game it will start the local login server and that is where it should redirect you to

Thats what I've done, but the redirect from the game opens the "Can't reach" website

Im gonna close this since its been months, I think this issue was due to some connection issue with your browser, if it still continues please open a new report