It was a broken camshaft. Had to get it fixed and cost me 50% the price of a new one. Didn't have much of an option, but this was helpful to confirm that I wasn't missing something simple.
I have a Toro 22" recycler, bought in 2017, and have changed oil and uses stabilized fuel over the recent years. Engine is Briggs and Stratton 128M02-0017-F1.
I tried to start it up this spring, and the engine didn't turn over after a few pulls, and then all of a sudden it started making this...