Does anyone have suggestions for alternatives for TestFlight that works on Android or iOS? This became more important since TestFlight announced it is dropping support for Android.
You don't need something like test flight for Android, as there is nothing special required to install an Android app on multiple devices. There is no concept of provisioning, etc.
You can install any Android App (packaged as an APK) on basically any Android device or emulator by copying it onto the device, and running the install command on it.
So, instead of TestFlight, you just need to provide a location to download your APK (basically from anywhere). You could make it available in a Dropbox folder, on a website (either something you create, or maybe the output page of your Jenkins\CI Server), via thumb drive, or even email the APK.
Bottom line, because Android does not have the same packaging restrictions as iOS, it is much easier to distribute test builds, so TestFlight (or equivalent), is not really necessary.