Well, you could use the wrong finger. After 3 attempts, my GrapheneOS install brings up the password field, but you can go back to the lock screen and try 2 more times until it locks out of fingerprint unlock (so 5 times total). You could always hold the power button down while it’s in your pocket or bag, pretending you are searching for the phone or something, and then lock it down as soon as you lift the screen up.
Well, you could use the wrong finger. After 3 attempts, my GrapheneOS install brings up the password field, but you can go back to the lock screen and try 2 more times until it locks out of fingerprint unlock (so 5 times total). You could always hold the power button down while it’s in your pocket or bag, pretending you are searching for the phone or something, and then lock it down as soon as you lift the screen up.