In order to keep our react-native app updateable and private, we decided to use this approach to upload an APK to the Play Store privately. Apparently, our client has to have G Suite set up for this to work. I suppose, with G Suite, the client can "add" user accounts to the company and with that, somehow allow them to download our app (by whitelisting it?).
But how/where can the Users download and install the private app after it has been published? Can they just search for it on the play store and see/download it there?