After several days of investigative work, reading hundreds of comments posted here and on Amazon, Best Buy, Houzz, Reddit, etc, I have solved my nasty tasting water problem with my LG refrigerator. I truly hope this is helpful to someone else experiencing this issue.
Have the LFXC22526 model (22.1 cu ft, french door, counter depth). Immediately after installation of water line and water filter (ADQ747935, LT1000P), and flushing with >3 gal, water had a noticeable chlorine/chemical taste. Bitter aftertaste. Not drinkable. Tap water has a mild chlorine/musty taste but this was significantly worse as far as bitterness and intensity.
LG instructions being posted on forums by the admins were not helpful. Tap water is "fine," filter brand new, water line fine, no odors in fridge, etc.
Water line was included with fridge, highly rated on Best Buy with >12,000 reviews. Considered looking into replacing it but did not. Stainless steel braided line intended for this purpose. (Smart Choice Model # REF 6FT WTR KIT). With that many positive reviews I excluded this as a factor.
Another posting on a different thread on LG website said the filter is just a dummy cartridge with no filtration properties and needs to be replaced with a new one, person said replacing the filter fixed their issue (I think a different action fixed their issue as I'll explain below). I was convinced this was the case and went out to buy another LG filter at $50. It's identical to the one that came with the fridge. Ended up not replacing the original filter because they are identical in every respect, other than the date of manufacture. Keeping the filter I just bought for 6 months from now.
Someone also posted on a different thread that their filter was dry and submerged it underwater to purge out all the air, saying the filter was "airlocked" which prevented anything from entering. This was also the case for me so I dunked it under water until all bubbling stopped. Was convinced I solved the issue seeing these bubbles! Couldn't believe LG would design a filter that needs manual purging, but I just wanted my problem fixed. Flushed another 3 gallons, water still tasted awful.
The fix ended up being exactly what "Shakes" alluded to in an LG forums post- the filter was not seated properly! Nothing was entering it, the water must have just been bypassing the filter the entire time. The key here is you push the filter in, twist to the right so it hangs onto the coupling, then TWIST HARDER to the right until it fully locks in place. There are 2 positions at which the filter will seem "seated," but it is critical to keep twisting the filter until you are in the second, fully locked position. It almost feels like you are applying enough torque to break the thing, but it doesn't break. Just twist firmly and slowly (no jerking motion) and you'll be ok.
After this I ran another 3-4 gallons through and the water tastes amazing! Not a filter problem, fridge problem, water line problem, or tap water problem. Vague instructions and no visual indicators leading to user error. If LG would put arrow markers on the filter and housing this could have all been avoided! Opportunity for improvement here...
Q