> But you can't verify that the open-source matches what's on the Play Store

According to their blog, builds are reproducible[0]. Am I missing anything?

> you can't link to the official server with your own build

Why not? (I know Moxie discouraged publishing custom builds while linking them against the official Signal server but this is not the same thing.)

[0]: https://signal.org/blog/reproducible-android/