Your options are building from source, downloading dev apks, or using an app store. If you can’t trust anyone, then you need to build from source

Fdroid is the best of the app stores, they are always trying to stay ahead of the curve when it comes to privacy, security, and trust

Reproducible builds are the standard for FOSS trust, see this article for an overview. They close the gap between app stores and dev apks

Fdroid are constantly working to increase the prevalence of reproducible builds, and to enable you to verify more so you have to rely less on trust