But this is completely impossible, and Google helps make it that way. Their SafetyNet API lets apps verify that the device is running an official, unmodified Android build, and a lot of very popular apps will refuse to run otherwise.
SafetyNet is also stifling innovation.
Linux/*BSD/macOS can run many Windows apps without emulation via WINE, and those innovations allowed Steam to create potentially billions of dollars in value by making many of their games cross-platform with Proton, and allowed them to create new products like the Steam Deck. SafetyNet precludes ever creating value like that with mobile apps.
Although they use emulation in WSL 2, Microsoft has done something similar with WSL and Linux apps, creating an untold amount of value for not only their platform, but for millions of developers, as well. SafetyNet prevents using something like WSL to run mobile apps on Windows.
For those reasons, you can't build an alternative OS and run many Android apps on them with a compatibility layer, despite apps without SafetyNet working pretty well using compatibility layers like Anbox.
I hate it when these fucking companies use cryptography to control us. Cryptography should be empowering us...
It's all so tiresome.