That's because google and samsung need each other. So samsung gets a pass. They don't allow other manufacturers.

Huawei ships with their own app store on devices with Play Services as well. There's no restrictions for other manufacturers.

What other manufacturers can't do is fragment the ecosystem and prevent people from also using Play Store.

The epic lawsuit has quite a few details about google preventing manufacturers from installing epic software/epic store on devices.

This still is a walled garden. Store from os or manufacturer. If you try to install a third-party you may end up with poor user experience from the os.

Time to split app distribution from OS. Making it mandatory to allow other stores, with first class user experience, and not set their as default one.

I installed the amazon app store on my android phone and it worked fine same with installing FDroid. all i had to do was check a box when prompted.

Sure but it's only you, already knowing about alternative stores, and with your specific device.