It’s been quite a long time since the last time new beta testers were added. Doing some digging, it looks like that new beta testers were added once per year, right around May-June each year. So, the last batch was May-June 2019.
That said, the testimonials for Redi in this thread are exceptional regarding the value he can add to the beta program. I’ll tip my hat in his direction as a candidate for the “Beta Class of 2020”.