From the start google has allowed alternative app stores on android, samsung phones come with the samsung app store installed by default and there are many, for example f-droid you can install yourself.
Now they will be forced to allow them on Google Play directly with user-friendly install.
I owned 2 Samsungs and that wasn’t possible on any of them. Either it wasn’t “from the start”, or it wasn’t on all models, or it involved rooting the phone first, which voids the warranty, at which point I wouldn’t count that as “allowed”.
But not through the existing app store, you have to go through what google termed "side-loading" which was pushed to be seen as "very dangerous thing no one should ever do no matter what"