Does it matter if they have 99% of the market? Apple and Google are both locking down the hardware so you can’t replace the OS. With Google you still have options like LineageOS but that might change soon. Android isn’t really open source. So what choices are left?

Would be nice to have iPhone-like hardware quality paired with a boot loader that lets the user choose between various free OS‘s that have compatibility with Android APKs. That would require a translation layer.