I have not successfully gotten BetterTouchTool's 1 finger middle click trigger to work. I am trying to set it to trigger a middle click.
I have also tried
magicPrefs.app (no longer supported)
middleClick.app (wouldn't show options in menu bar)
Middle.app does work perfectly, but I would rather use better touch since it is another paid app I shouldn't need. Found here: https://ryanhanson.dev/
using iMac 27" OS10.15.7
With magic mouse 2
betterTouchTool 3.5.04