I see a lot of text here describing a problem that really could have been explained in two sentences, and even more text expressing your frustration. And yes, I can understand that to some extent, but unfortunately, that’s not really productive.
If instead of writing out your story of suffering you had filled out the support template and provided logs, someone might actually have been able to help you. I mean, you didn’t even mention what version of the client caused the issue.
Could have been this issue, which apparently has already been fixed: https://github.com/nextcloud/ios/issues/3655