I tested several third party app stores. But found direct download of the APK from https://stashpay.me had the best UX. The APK is signed with the developer key. So it‘s a TOFU (trust on first use) model if you trust the TLS cert on the first install. Subsequent updates of the APK would verify the developer signing key.

What‘s the advantage of using third party app stores? They don’t do auto-updates as far as I understand?