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Beeper vs Apple battle intensifies: Lawmakers demand DOJ investigation - Android Authority
(www.androidauthority.com)
This is a most excellent place for technology news and articles.
Encryption extension on RCS is a non-standard addon to RCS which is not part of the standard. RCS on Android in general is also run through google servers and Jibe, and isn’t exactly an open standard to begin with.
Apple isn’t preventing cross platform encryption at all, every popular messenger (even Signal) is available in the App Store.