Taking it outside of the walled garden should always be Step 1 for apps like this. PWAs exist, and most users these days have seen the "Add to Home Screen" prompt on websites. There is no reason for this to be a native app.

> This is particularly worrisome because for most people Google Play is the only way they understand to install apps at all.

I disagree. Users dependent on installing apps are the least likely to use fediverse apps to begin with. I use F-Droid or download APKs from XDA, but I have no idea how I would even get started with Mastodon or these other decentralized apps. I frequently hear the term "start an instance of ___".

What does that mean? Can't I just create an account? When I hear "start an instance", I think of launching a Linux droplet on Digital Ocean and setting up an app there. I can't imagine what an average user that wants a Twitter alternative would think.