So I just installed/upgraded to the public beta for macOS, which has gone smoothly apart from my Duet app not working any more (iPad app said connecting constantly).
As Sidecar is a new feature of Catalina, and I have a compatible Mac, I removed duet but then found that I was unable to find sidecar on MacOS Catalina, Check against the requirements list and I should have it...so the real question is, why don't I?
My Macbook Pro is the 13" MacBookPro 14,1 (2017) with an iPad Air 2 (connected via a USB-C->USB 3->Lightening connection.
Before I upgraded, Duet was working perfectly.
