This article sheds light on using feature toggles to control beta releases and target specific users:
To overcome these challenges, smart product teams are beginning to run betas with feature flags/toggles. These are mechanisms for granularly controlling software releases, allowing you to control the timing and visibility of a beta release.
Currently, many betas are tied to code releases and are managed by a config file or database. This approach requires engineering time or custom mechanisms to opt-in users.
With feature toggles, you can empower product, marketing, sales, and even customers (themselves) to opt-in new to a new beta experience.