I've connected 2 macs with joplin to my nextcloud already and it works fine. But the joplin app on android failed to log in. Am I doing something wrong or is there a bug? Tried the following URL's:
Also you should double check your URL because the message "not a valid URL" really means what it means, that it's generally not valid (not just as a Nextcloud URL). Perhaps there's an extra space or something in it.