Product review (4 stars): Whirlpool Water  EDR4RXD1 (UKF8001) - replacement filter - CGP (Certified Genuine Part)
I just received the filter today.  It gets 4 stars out the gate.  In order to get the fifth star, it actually has to work for a while.  I checked the Whirlpool site for my model refrigerator.  The former filter part was UKF8001.  The new filter part is EDR4RXD1.  I ordered EDR4RXD2, which includes 2 of the filters.  The old UKF8001 took a bit of twisting to get out.  I do this infrequently, and I guess the plastic in the filter had bonded to the rubber and plastic in the refrigerator holding assembly.  Finding the right amount of force took me a minute.  I had pre-filled the new filter with water.  Neither the manual nor the YouTube video say to do that, but I read another Amazon review where someone mentioned having done so, and it made sense.

I almost bought aftermarket, but there were mixed reviews, including some discussion about problematic rubber gaskets.  So, I bought the genuine CGP (Certified Genuine Part).  The new filter went in just fine.  The water flowed clear and strong.  I ran about 2.5 gallons of water through the water dispenser.  The manual says to run for 2 minutes.  The water flowed clear for the entire 2.5 gallons.

So far so good.  Everything is working.

Notes from the packaging:  This is referred to as an "everydrop" filter.  The filter is also referred to as "Filter 4: EDR4RXD1 (UKF8001) - replacement filter, Replacement Cartridge UKF8001 for System Models UKF8001AXX-300 & 67003523-750)", which is interesting as web searches for UKF8001 refer to two separate ratings, 300 gallons and 750 gallons.  This packaging specifically states 300 gallons, replace every 6 months, "Contaminant reduction declines after 300 gallons".