Valve exists but Valve's alternative is way pricier and requires a computer right? Facebook would be able to mass-produce these devices at a low cost in a completely different way it seems.
So since it is an android system under the hood it would be very possible to make VR apps that would work on all android systems. This would be so much better for the ecosystem as a whole.
Surely there are WebXR standards that would basically be webapps so they would be totally platform independent however this will surely not cut it for all applications.
Seeing how social media companies can manipulate politics and steer behaviour through ads imagine what happens in a VR only reality. This is a total nightmare scenario.
Would it be possible to try to create some sort of campaign to make people more aware about the bad effects of this lock in. Perhaps by finding a suitable chinese device that remains open and try to favour that over facebooks versions. Sort of how Huawei managed to more or less copy devices at a lower costs and get into the market that way?
Microsofts Mixed Reality standard deserves some attention as well obviously. Again this requires a PC and they seem to be a bit more pricier as well. These wouldn't require base stations as well.