I am having an issue with Nextcloud 16.0.1 (it’s always been an issue regardless of version) and Mobile devices and the desktop app. I do believe that this is related to my HAProxy Loadbalancers since the issue does not occur when I have one of my Nextcloud servers removed from the cluster. Logging in is NOT an issue when using Android browser or desktop browsers.
Do any of the Nextcloud Apps (IOS/Android, Desktop) obey or receive/hold cookies? My loadbalancers send cookies to users to determine which server they are on as to keep sessions stickied to a specific server. When logging in to my nextcloud in the mobile app, the requests bounce back and fourth to each server in my loadbalancer and end up failing because the entire login sequence is not sent to just one server.
It ultimately sends the user into a login loop where it attempts authentication, asks to grant access, then sends you right back to the login prompt.