I know that the HN crowd has a weird relationship with both Apple and Google that go in two very different directions regardless of the evidence but honestly I think what you are proposing is actually a really good long term plan.

Flutter is currently rewriting a key part of their graphics rendering pipeline as we speak that should clear up the remaining issues people seem to have with it when it comes to performance and the rest of the project is incredibly well supported and documented and most importantly as you hinted at genuinely cross platform.

It’s a much better bet for basically any project outside of one that you know for a fact is only ever going to target Apple operating systems.