How to remove bathtub drain flange with nubs?
You CAN use Channellock type pliers, just not the way in the linked picture/answer shows. You use the handles of the pliers, adjusted to the width of the throat of the tub drain, as spanners. Insert the handles into the drain so they are against the nubs, then turn those pliers by putting a pipe wrench, large adjustable wrench, or another set of pliers on the jaws of those pliers (which are pointing up) and turn counter-clockwise.

I have removed numerous tub drains using this method.