I personally believe the most logical, and long-term sustainable solution with the most control to the "Android becoming more closed" threat, is to fund and support @postmarketOS and alike initiatives.

a fully decentralised solution developed by the whole FOSS ecosystem together is infinitely better than depending on the whims and generosity of big tech companies.

And, they still get to support the ecosystem by committing Linux/etc patches upstream, it just has better power balance in the end.