I've been thinking about this for a very long time. The only platform that actually passes all of Soatok's tests is Simplex. But it's only briefly mentioned in the article about session

(For example: SimpleX was audited in December 2024. Don’t ask me about SimpleX, you have a goddamn report from professionals I respect right there.)

Wait no. I think only server builds are reproducible.

But there is an Android build on F-droid and F-droid does offer reproducible builds, so that's a way to get them.

A big problem, however, is that the creator of simplex is an antivaxxer, anti-DEI, anti-abortion, climate change denialist, etc. I can understand why people would be hesitant to push a platform like that, given they may also be pushing the creator's beliefs. I think it's okay to do the recommendation with a little asterisk of "please be aware that the creator of this app is crazy".