You can install Android yourself. Most people will use Android "distros" like https://lineageos.org/ https://lineageos.org/. Or of course you can go the "Androi

You can install Android yourself. Most people will use Android "distros" like https://lineageos.org/ https://lineageos.org/. Or of course you can go the "Android from scratch" route. But yes, the biggest issue is drivers. Many phones have proprietary drivers that are required for the hardware to fully function.