Three-finger tap for Lookup not working on Mac mini M6 with Magic Trackpad 2

Ok, found it. Under Accessibility -> Zoom, 'Use trackpad gesture to zoom—Double-tap three fingers to toggle zoom' was toggled on. Thanks for your help tracking down this issue.

The three-finger tap gesture for Lookup failing on a desktop Mac while working via right-click and in Safe Mode points to a configuration conflict, a specific trackpad setting override, or a Bluetooth driver glitch unique to the Mac mini setup.

You can troubleshoot and fix the issue using these steps:

Toggle Off and On the "Look Up & Data Detectors" Setting

Sometimes the macOS preference flag gets stuck even if the toggle appears active.

• Go to Apple menu  > System Settings > Trackpad.
• Under the Point & Click tab, find Look up & data detectors.
• Change the dropdown from Tap with three fingers to Off,
• Restart your Mac
• Return to the settings pane and switch it back to Tap with three fingers.

Check for Gesture Conflicts (Three-Finger Drag or Accessibility)

If three-finger drag or another accessibility/window management feature is enabled, it can override or block the tap-to-lookup gesture. 

• Go to System Settings > Accessibility > Pointer Control.
• Click Trackpad Options...
• If Use trackpad for dragging is ON and Dragging style is set to Three-finger drag, then disable Use trackpad for dragging to test if it frees up the gesture. 

Unpair and Re-pair the Magic Trackpad 2

Since this is a desktop Mac mini rather than a laptop, Bluetooth device pairing states can occasionally drop specific multitouch event mappings.

• Go to System Settings > Bluetooth.
• Hover over your Magic Trackpad 2, click the Disconnect / Forget option, and turn off Bluetooth for 10 seconds.
• Plug the trackpad in directly via its cable to re-establish a direct HID pairing, then test the three-finger tap again.

Reset the Trackpad Property List (PList)

If a preference file is corrupted on the Mac mini (which wouldn't clear if you tested a fresh user or if the plist carried over), deleting the preference file forces macOS to rebuild it.

• Open Finder, press Cmd + Shift + G, and paste:

~/Library/Preferences/

• Look for files starting with com.apple.AppleMultitouchTrackpad.plist and com.apple.driver.AppleBluetoothMultitouch.trackpad.plist.
• Move them to the Desktop (as a backup), and restart your Mac mini (macOS will recreate them, you will need to restore your desired trackpad settings).

More info from Apple: Change Trackpad settings on Mac – Apple Support

Personally, setting Look up & data detectors works as expected when set to Tap with three fingers on my M4 Pro MBP when tapping on an external Magic Trackpad 2 (I usually work in clamshell mode).

In System Settings > Trackpad, have the click adjust set at least to here:

If the click slider is less than shown, my three-finger tap will not select a word, and as shown, the same word presents the expected lookup display. The alternative is the control+cmd+D keyboard shortcut with the pointer poised over the (unselected) word.

The order of the dictionaries configured in the Dictionary application's toolbar will be the top down order shown in the above lookup result.

If you did not previously set this Accessibility -> Zoom feature, then this is another case of Apple imposing unwanted preference settings in the macOS updates.

Good find. Will help others in the future…

These are my settings. I believe everything checks out. These match the settings on my MacBook Air

Good work tracking it down! There are several similar 'conflicts' that can arise with those gestures.