Answering the original question - I just tested this in Safari and Mail.app to force links to open in Chrome - works for me on MacOS 11.5 and BetterTouchTool 3.570.
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Pick a trackpad trigger.
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Assign the "Trigger Context Menu Item" action. In the text box, specify that you want it to "Copy Link Address" to put put the link on the clipboard.
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Under the pulldown menu where you've selected "Trigger Context Menu Item", click "Add Additional Action"
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For the second action, select the "OpenURL with Browser" action. In the text block where you specify the URL to open, specify %@ and then choose the browser you want from the menu lower in this screen. Click save.