I have been playing with the Mindstorms Robot Inventor kit (#51515) for some time. Unfortunately, it does not have a display, but it has 25 LEDs. The battery level can only be viewed on a connected device: laptop or smartphone. I wrote a short Python program that lights up 3,5,10,15,20,25 LEDs depending on the battery level. It can be uploaded let's say as the 19th program and it will stay in the hub. Maybe it will be useful to someone. Any comments and suggestions are welcome.
Battery level on Mindstorms Robot Inventor