Audacity 4.0 shipped today, rebuilt on Qt with clip-based editing.

The 4.0.0 tag published September 3 at 10:19Z, a full UI rewrite on Qt with native high-DPI support, customizable workspaces, themes and a recent-projects home screen. Editing moves to a clip-based model with multi-clip selection, grouping and an S-key split tool, plus seekable playback, recording at any timeline position and ASIO in Windows builds. Projects move to .aup4 with automatic conversion from .aup3. Time Tracks, MIDI, the Mixer and Play-at-speed are all missing from 4.0, so don't upgrade a working workflow yet.