I'm pretty sure their goal is to support every Android device possible eventually, but those Tab A devices all run old versions of Android as far as I'm aware and that could be an issue in the end.
For now you can check your Stadia app settings. Go to the Experiements section and enable "Play on this device", it may already work fine even if not officially supported. Doing this allows me to play Stadia perfectly on my phone even though it's an unsupported model, but YMMV.
