This 5-year old Note 10.1 (2014) AIO recently got replaced so I decided to use it exclusively as a 2nd display monitor via Miracast from my work Surface 3. It now has pride of place on my desktop.
The app used on the AIO is "Airscreen", available from the Play Store. Supports Cast, Miracast, Airplay, dlna and a few more in the paid version.
And this is the replacement:
1. Galaxy Tab A 8" w/SPen (2019) LTE paired with:
2. a Surface EMR Pen,
3. a MS Wedge BT Mouse &
4. a generic BT Keyboard with trackpad.
I am loving this little machine. OneUI is excellent with OneHandOperations+ installed & navigation bar disabled.
The only caveat is battery life. With BT, LTE, location & auto-sync on, I barely get thru a full business day the first couple of days. I topped-up during lunch to get me to EOD.
It is a daily charge tablet, no doubt. Other than that, it an excellent AIO as a daily work carry. The portability is something I have missed coming from a Note 10.1 (2014)
For the price I paid, it is well worth the investment, imho. Just wish that there is an 8" Tab S6 counterpart but I wager the price will be doubled or more if it comes to pass.
Other uses:
1. Sidesync with Surface 3 for Keyboard & Mouse screen-sharing.
2. Screen-mirroring via Smart View (Miracast)