Here are a few features that would be great to have in the iOS client.
Integrate the login with 1Password.
They have drop in code you can add to the app so that when asking the user for the credentials, there is a small 1Password icon in the field that they can click to switch over to 1Password, select their odrive entry, and it puts in the username/password automatically.
Being a 1Password user, my odrive account password is 20 random characters so there is no way I’m going to remember it and be able to just type it into the app.
Lock or auto-logout security
After a duration or if the app is quit, it should lock/logout and require authentication again. So far it appears that the app remembers the credentials and shows the files even if I force quit/kill the app.
After the user has authenticated, offer the option of using TouchID/FaceID (if the device supports it) for future logins. This would be a big plus if you add the auto-logout/lock feature.
For a good example of the last 2 features, take a look at the 1Password app itself.