here's how to use your Android tablet wirelessly as extended screen to your Mac (free and better than Duet Display)

I was looking for a solution. Not just mirroring but using the tablet as an external display to Mac.

Duet Display is a paid option but my experience was not good even with wired connection. Then, I came accross this old thread: https://www.reddit.com/r/GalaxyTab/comments/13m2u0l/second_screen_macos_to_galaxy_tab_s8/

I tried u/Quadfadder's suggestion and it worked flawlessly.

It's great. Free, open-source and works wirelessly. It can work with any device with a browser not just tablets. Experience is so much better than Duet Display even though DD is paid.

How to use it?

The app's name is Deskreen (https://deskreen.com/lang-en)

It mirrors your screen but if you need second screen feature, it suggests a virtual display driver dongle (it's cheap). If you don't have a virtual display driver, then you don't have to buy. You need to also use this with the app:

DeskPad (https://github.com/Stengo/DeskPad)

Just open Deskpad, it will create a virtual display.

After opening DeskPad, open Deskreen, make the necessary connection and when selecting which screen or application you want to share to tablet, select entire display and select the one DeskPen provided. It should appear in there. AND if it does not work, try playing with DeskPen's dock icon's right click menu options.

Thank you u/Quadfadder for suggesting it and thanks to the developers of Deskreen (https://github.com/pavlobu) and DeskPad.

Note: If you are a Windows user, you can just use Samsung Second Screen. Unfortunately it's only for Windows.