It looks a lot like a watering issue - either too much or not enough. The symptoms are similar for both situations.

Lilies are not really houseplants. They are often sold as potted plants in bloom or heavy bud for a touch of indoor color but they will not last long indoors. If purchased for this purpose, they need to be kept cool, with bright but not direct sunlight and the potting medium should stay just barely moist to the touch. Overwatering can cause the roots to rot, causing symptoms such as your plant shows, and underwatering or allowing the soil to dry out completely can do the same.

The plant is not going to recover so you might as well cut your losses and discard.

This is the natural progression of this type of lily and it isn't anything you're doing wrong...it's not going to get green again right now. If you want to AND if the bulbs are still good (not mushy) AND if you have someplace to plant them in the spring, put the pot somewhere cool and dry (such as the basement) and cut the stems at soil level after they've all turned brown. Note: at this point, as long as the soil isn't wet, I like to put the pot in a dark ventilated plastic bag or cover with a larger plastic pot w/holes. Remove from pot and plant in the ground as soon as your soil is workable in the spring.
I've never tried to rebloom a potted lily in the house. Maybe someone else can give you suggestions for that.

Am I correct in assuming from the linked post that the flowers never opened? Wondering whether there was some chemical/forcing shenanigans going on from the grower....

Besides this forum and the lilies forum, the same query is posted on the Trees Forum. All have been responded to by other posters in one fashion or another.

Not sure if we're missing the answer the OP wants to hear.

Basically: hybrid lilies aren't really houseplants. They tend to thrive best planted outdoors in the ground.

The examples shown in the OP's post were likely way past prime when purchased and Big Box clerks often know squat about plants. Inside didn't provide the conditions needed and the lily started the decline before the buds opened.

Done for this season - if the bulb(s) is firm and free of any rot, might be salvageable for next season out in the garden.