I doubt Steam will provide an official way to piggyback on the Meta store, mostly for legal reasons. I imagine one will, like today, add external games to Steam and instead of using Proton will use Lepton.
It's possible to get all apks of Meta store by sailing the high seas.
but it tapers off very quickly, namely setting up the gateway might take half a day, pairing the first device might take an hour... but then the next 10 devices will probably take 10min.