Took a punt at this, and wasn't too bad. Does everything I need it to do, Very handy for portable dual screens!
Obviously some might have a different experience.
Works with both Windows and Mac (Using is on win 10 currently). Only about 30 min into using it, but seems to be 'minimal' lag not zero, but that may be due to the low power integrated GPU I'm using it with.
app description:
Duet turns your iPad or iPhone into the most advanced extra display for your Mac & PC. Developed by a team of ex-Apple engineers, Duet offers unparalleled performance and display quality - all with zero lag.
— DO MORE —
Be twice as productive by multitasking with two screens. And for those that travel, have a portable way to stay productive.
— INCREDIBLY SIMPLE —
To get started, plug your iPad into your desktop using your charging cable. The free Duet desktop app will automatically detect your device, and transform it into a high performance touchscreen display.
There’s no need to worry about unreliable Wi-Fi, laggy performance, pixelated screens or managing network passwords.
beware, app on windows messes up with nvidia drivers