Samsung yesterday announced the launch of the beta testing program for the One UI 4.0 proprietary shell for Galaxy S21 smartphones. And despite the fact that the entry was soon deleted, it may indicate the imminent start of testing a new firmware based on Android 12.
— Ice universe (@UniverseIce) July 28, 2021
Sammobile reports that Samsung will begin rolling out the update to beta testers in September. The first wave will include the Galaxy S21, Galaxy S21 +, and Galaxy S21 Ultra models. Owners of Galaxy S20 smartphones will receive the test firmware in October. But the stable version of One UI 4.0 should be expected closer to December.
You can register for the One UI beta program through the Samsung Members app.