Just like the title says, Nintendo will be holding a closed beta for Mario Kart Tour on Android between May 22 and June 4. You can sign up to participate in the beta from now and until May 7 at 7:59 p.m. PT, and participants will be chosen randomly if too many sign up. Only the United States and Japan are being included in this, so my condolences to fans on the rest of the planet.
Typically, and for practical reasons, apps hit the Apple Store before they find a home on Google Play. So to even see a beta appear on Android over Apple Store is kind of refreshing, actually, in an arbitrary way.
Let us know if you sign up for the Mario Kart Tour beta!