as everything relevant is already said BUT the necessary attention is missing, I´d like to directly point to those two issues on Github, which seems to be the wrong place as lack of response and interest of capable developers is showing. Therefore I want to raise awareness from a user point of view.
This problem kills almost every producte interaction with nextcloud on the go. Fallback to the web browser is just a very bad workaround. Nobody takes care, this bug exists for 2 and 1/2 months now.
I´m not 100 % sure if the ball lies in the field of the iOS app team or the server team (especially the authentication, maybe even 2FA part of nextcloud server).
If money helps: who needs how much to take a look into this and fix it? We´re quite desperated.