Excalibur works both on macOS (10.14.5 and higher) and Windows.
Premiere Pro CC2019 support is being tested.
Premiere Pro 14.1.0 is not supported due to API bug. Whenever you will launch Excalibur, Premiere will crash.
Premiere Pro 14.3.0 "Export Media", "Export Selected Clips" commands won't work due to API bug.