Let's say you're running Raspbian on your Raspberry Pi 4 board, but would like to check out the latest Ubuntu 19.10 for the board. What would you normally have to do?
After downloading the firmware and turning off your Raspberry Pi 4, you'd normally need physical access to your Raspberry Pi 4 to remove the MicroSD card, insert it into your computer and start balenaEtcher or other utility to flash the image. Once it's done remove the MicroSD card from your PC and insert it back into the Raspberry Pi SBC, before booting it up.
That's fine for