Need Some Education On My 1991 Lincoln Memorial Cent, Is It Zinc Rot, Lamination, Finger Feeder?

Maybe there is a tiny die crack from the rim through the letter U, but the bulk of that looks like a linear plating bubble to me.

roller lines, linear plating bubbles that are following the roller lines.
the one over 'Trust' looks to have cracked open.

Here's the best explanation I can offer. Others may have different or better explanations for it, and my explanation and a dollar may get you a half cup of day old gas station coffee, so take it with that caution.

IMHO, they are a little bit different and may result from the same events, but at different lengths of time after minting.

Zinc rot is subsurface corrosion, caused by something that interacts with the zinc itself over time, and pushes the plating up after the coin is struck. In other words, whatever interacts with the zinc isn't by itself making what we see, but the eventual interaction of that substance with the zinc damages the zinc core itself, causes it to expand, and results in the ugliness we call zinc rot. The rot seems to appear on coins that have circulated for some time and also on coins that have been exposed to heat or environmental damage after minting. Environmental exposure includes the Katrina coins and Harvey coins, which were exposed to the toxic soup of the flooding in those hurricanes, and then acid-washed to be put back into circulation.

The plating blisters of all types seem to be caused by gas bubbles. Exactly how and when in the process those bubbles develop is a good question. The bubbles seem to appear on fairly freshly minted coins, so they either could be earlier results of what becomes zinc rot or something completely different. ARTAZN's plating method is a trade secret, so one of the guesses is impurities in the preparation of the core for the plating.

Your coin has a bubble / blister that hasn't ruptured. Other coins have ruptured bubbles.

That's the best I can add to this.

Interesting example.