Two files, nothing to build.
On the Mac — download TabScreen-mac.zip, unpack, drag TabScreen.app into
Applications. The app is not signed with a paid Apple certificate, so the first launch
needs a right-click → Open instead of a double-click, and macOS will ask once for
screen recording permission.
You also need BetterDisplay (free) — it
creates the virtual screen, which macOS has no public API for. TabScreen can set it up
for you: press Create virtual screen.
On the tablet — download tabscreen-android.apk straight to the tablet and open it.
Android will ask to allow installing from this source. No developer mode, no adb.
Then press Turn on on the Mac, and the tablet finds it by itself.