Maybe you're advocating that, but -- even as someone who is generally skeptical of corporate power and the presumed wonders of the marketplace, and more amenable to reasonable government regulation (as subjective as that clearly is) -- this sounds like a pretty dubious idea.
The government regulation that might be called for in situations like this is regulation that puts a few limits on corporate control of massive platforms, not regulation that just transfers that control to other entities. Make locking down platforms too tightly illegal: relax laws about reverse engineering, mandate side-loading. I don't think we need to take away Google or Apple's rights to say what they will and won't sell in their own digital storefronts, but I don't think those rights should necessarily extend to control over what users install on their own devices. The problem is when those are the only legal storefront (e.g., Apple's iOS App Store), or other storefronts are highly undiscoverable.
So now, in the case of Android, the complaint is that the alternatives don’t know how to market. Should we also break up the record labels and the book publishers because you can’t easily discover independent authors and musicians?
The government regulation that might be called for in situations like this is regulation that puts a few limits on corporate control of massive platforms, not regulation that just transfers that control to other entities. Make locking down platforms too tightly illegal: relax laws about reverse engineering, mandate side-loading. I don't think we need to take away Google or Apple's rights to say what they will and won't sell in their own digital storefronts, but I don't think those rights should necessarily extend to control over what users install on their own devices. The problem is when those are the only legal storefront (e.g., Apple's iOS App Store), or other storefronts are highly undiscoverable.