Is there a way to use a pi-top  case without pi-topOS? Can I use different OS, for ex. Raspberry Pi OS 32-bit or 64-bit, and install apps/libs/scripts for pi-top  hardware?
You can use it with another OS but you’ll lose the hardware drivers, such as battery readings, soft shutdown, OLED screen functionality etc. We don’t currently have the drivers available as Debian packages but it’s on our roadmap to do so - we’ll also be making our Github repos public very soon so that others can contribute to the effort!