I think the whole UI has to be redesigned, but not in the same way as Android or IOS. Instead, a desktop OS approach just like on Linux, but compressed in a mobile format. That way the phone can be intuitive both when used as a phone and while docked.
So how to do that? Easy:
1. Make the dock behave as a desktop dock.
Instead of pinning apps there, make it show apps that are opened, just like on a desktop. That way you lose the whole "swipe up to check your open apps" thing while remaining intuitive to use. That doesn't necessarily mean you can't pin some apps there though, but it should be optional - just like on a desktop.
That way, clicking an app on the dock can maximize/minimize.
2. Use the Ubuntu button as a start menu/app drawer button.
You click it and the app menu opens. It can be separated in sections depending on the type of apps too. Pretty much the same as on Linux Mint. Clicking the button again closes the "start menu".
3. Allow adding apps to the home screen, like on a regular desktop.
I don't know why this isn't a thing. This compensates the changes in the dock. Allow grouping apps in folders too, etc.
4. Move the status bar to the bottom of the screen.
That way you solve the problem with camera cutouts and align the concept well with the gestures I suggest.
4. Gestures:
Left swipe to show dock in an app is a great choice.
Right swipe is now free, because the dock shows all processes instead. It can be used to return to the desktop instead. Long swipe can kill the app.
Down swipe can be used to open notifications.
Up swipe can extend the status bar and extend into a control panel - WIFI, Bluetooth etc.
This solves your home screen dilemma and is a good way to improve the UI of the OS.
