The fullscreen mode was added to Locus when Android did not support a translucent status bar and navigation bar. Both system bars were pinned to the screen without the possibility to style them. The only option was to hide them to increase space for application (fullscreen mode).
Over time, options to style system bars were added, and also from 2018, there are many devices with the notch, which are unusable with fullscreen mode, because some important UI elements are hidden behind the notch.
So we decided to delete fullscreen mode from the application and improve UI in map screens, so the map is properly visible behind system bars in both orientations. On other screens, the fullscreen mode does not make sense at all.
This solution is also correct in terms of Android recommendations.