The side of the analog stick reads: 2124IC.

The analog sticks are frictionless and use green potentiometers, not sure if these are ALPS potentiometers similar to those in the Xbox series controllers.

The blue circle next to this stick is the trigger's hall-effect sensor which senses the magnet installed on the side of the trigger. The other sensor is mounted similarly on the opposite side of the board near the B button.

The middle of the daughter board has an adhesive strip covering some of the solder joints and a few test points. Perhaps some isoprophyl alcohol can soften the adhesive to remove the black strip if necessary.