>broken SGX metadata protections
Citation needed. Also, SGX is just there to try to verify what the server is doing, including that the server isn't collecting metadata. The real talking is done by the responses to warrants https://signal.org/bigbrother/ where they've been able to hand over only two timestamps of when the user created their account and when they were last seen. If that's not good enough for you, you're better off using Tor-p2p messengers that don't have servers collecting your metadata at all, such as Cwtch or Quiet.
>weak supply chain integrity
You can download the app as an .apk from their website if you don't trust Google Play Store.
>a mandate everyone supply their phone numbers
That's how you combat spam. It sucks but there are very few options outside the corner of Zooko's triangle that has your username look like "4sci35xrhp2d45gbm3qpta7ogfedonuw2mucmc36jxemucd7fmgzj3ad".
>and agree to Apple or Google terms of service to use it?
Yeah that's what happens when you create a phone app for the masses.
