3
Signal Alternative with SMS Support
(sh.itjust.works)
F-Droid is an installable catalogue of FOSS (Free and Open Source Software) applications for the Android platform. The client makes it easy to browse, install, and keep track of updates on your device.
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But it's not E2E encrypted
That's because SMS isn't end to end encrypted in general, you need a encryption client on both sides to achive E2E encryprion aka Singal to Signal or something comparable.