SUMMARY Sidecar is a new feature introduced by Apple that allowed Mac users to do the same thing with their iPad. Users can use iPad as a second display that is perfect in the office or on the go, and using Apple Pencil for tablet input on Mac apps for the very first time. With help of this feature user could making use of iPad and Apple Pencil to preview and edit the image. STEPS TO REPRODUCE 1. None OBSERVED RESULT EXPECTED RESULT SOFTWARE/OS VERSIONS Windows: macOS: Linux/KDE Plasma: (available in About System) KDE Plasma Version: KDE Frameworks Version: Qt Version: ADDITIONAL INFORMATION Apple's whitepaper: https://www.apple.com/macos/catalina/docs/Sidecar_Tech_Brief_Oct_2019.pdf
I'm sorry, but that's not part of Krita, but part of Qt. In fact, if sidecar integrates with the native macOS support for tablets, then it should already work, as noted in that pdf: "Apple and third-party Mac apps that support stylus input already work with Apple Pencil, " Have you tested this? We cannot test it, because our macs are too old to support sidecar.
Sidecar works on krita already. this can be seen here: https://youtu.be/7ROc8dMDams?t=494 The problems shown in the review are also seen in Photoshop and Affinity Photo.