> there is never an alternative offered which my grandma could use

E2EE messenger Wire comes from the people who created usable Skype and contributed to the royalty-free audio codec Opus (https://opus-codec.org/) which now enables WebRTC (used by modern conferencing apps including Zoom, Jitsi, GoToMeeting). They contributed to the IETF encrypted group-messaging protocol MLS (https://datatracker.ietf.org/wg/mls/about/), which has been ratified and lives alongside TLS.

IETF MLS is one step on a long path to messenger interoperability, e.g. Matrix plans to implement MLS. Contributors to MLS include Apple, Cisco and Facebook.

Unlike Signal, Wire never mandated disclosure of phone number or address book contacts. Their business model is paid enterprise customers, but they continue to maintain free clients for iOS, Android and web, with open-source client and server code.