Matrix has E2EE support and many clients are pushing it as the default. But it also supports rooms that are only encrypted in transit.

That's correct, but E2EE also allows for unverified devices[0]. Key distribution and device verification are separate issues, and the former doesn't enforce the latter until April 2026 as they've announced in the HN article.

[0] https://matrix.org/docs/matrix-concepts/end-to-end-encryptio...