Even if you managed to find an old beta installer file, you would not be able to play it because the servers required for those builds were shut down to make way for the full launch.
: All participants were required to register a Capcom ID and link it to their platform (Steam, PSN, or Xbox Live).
Capcom has rotated between closed and open betas. For the next closed test:
The official Street Fighter 6 Open Beta tests were limited-time events that took place prior to the game's global launch on June 2, 2023
If you have been granted access and the beta weekend is active (e.g., Friday 7 PM PT to Sunday 11 PM PT), follow this to use the correctly: