I had stopped using duet on my 2017 iPad because it will not charge while connected. Just tried it again with my 2018, it will now charge while connected. However, the touchscreen doesn't work. The touchscreen used to work, you could essentially run Mac apps with a touchscreen interface. It appears that no longer works, duet lets the iPad work as a second display, but only with trackpad support. I'm not going to use duet because it doesn't support touchscreen anymore and the connection is flaky and disconnects after like 5 seconds if you switch to another app on the iPad. Duet "works" but because of these problems it is not useful to me.