Safari DP 141 actually released RTCRtpScriptTransform support 2 days ago (thanks to https://trac.webkit.org/changeset/270107/webkit/). But we're waiting eagerly for Firefox to add it in https://bugzilla.mozilla.org/show_bug.cgi?id=1631263.

Hopefully by the time we've sorted out the SFU component, all the browsers will have RTCRtpScriptTransform implemented and so we'll get good cross-platform E2EE for larger calls (rather than it being limited to Chrome + Safari + Desktop)