Honestly I would use a stupid basic one that someone might try and use if they were guessing. Like a duress pin of 1-1-1-1, 1-2-3-4 or 2-4-6-8. It gets the people who take the device and then try and break into it without your permission as it’s almost certain they will at least try one of those three.

Worst case scenario they ask you and you say what it is and they give you a blank stare of “really?..” it’s not like they wouldn’t try a pin you gave them.

I don’t recommend a duress password of 1-1-1-1, because that could be set off accidentally.

Or those common dumb ones could be attempted by someone just trying to snoop on your phone.