Hi there!
i’m not sure what category to choose and if this is even the right forum 
i’m a longtime and happy nextcloud files user, the server installed on my webspace and clients on all my computers and on my iphone. in the last years there was an option in the iphone app to encrypt a folder, specifically and only accessible on the phone. that i really enjoyed and used it to save sensible data. Since the last update the option is gone somehow. did you take that feature away from nextcloud on iphone? or is there some setting wrong?
cheers, henrik