Chromium gates the PulseAudio loopback path behind the
PulseaudioLoopbackForScreenShare feature flag. Without it, returning
audio: 'loopback' from setDisplayMediaRequestHandler rejects the whole
getDisplayMedia request, so screen share never starts when the user has
"Share system audio" enabled. Also surface a clear warning toast on
loopback failure (PipeWire-only without pulse compat, macOS without
Catap) instead of failing silently — no auto-retry, since the picker
selection is already consumed.
Jannis Braun
f538f1d92e