The interface (mic, cam, hangup etc. buttons) on the bottom and session name and time on top of the page do not disappear when using a mobile browser (tested chrome/android and safari/ios).
Desktop browsers work as expected.
As far as I remember, this did work before.
Probably it broke when moving the settings from interface_config.js to config.js.
I tried the “old” settings in interface_config, but it made no difference.
The behavior can also be seen in sessions on https://meet.jit.si.