> HSTS preloading blacklists may at some future point, block PWA as well.
What on earth are you talking about?
1) As far as I am aware, there is no "HSTS preloading blacklist". I'm not sure what that would even mean.
2) HSTS preloading is not a prerequisite for creating a PWA. Nor is presence on the HSTS preload list (not "blacklist") an obstacle to creating a PWA.