System-wide/background push-to-talk (PTT) voice chat without registration or having to run my own server (to replace Discord)?

Jitsi Meet and Matrix are missing system-wide/background push-to-talk (PTT) (to replace Discord).

• Tell Jitsi -> github.com/jitsi/jitsi-meet-electron/issues/210

• Tell Matrix -> github.com/element-hq/element-web/issues/15284

• Tell Element Call -> call.element.io (Settings > Feedback)

• Tell SimpleX -> github.com/simplex-chat/simplex-chat/issues/2398

Alternatives (obviously must be cross-platform end-to-end encrypted libre software)?