What suggestions can you make for an OTC knee brace that relieves discomfort more than it generates it?

None in the OTC space.
See your orthopedic Dr for a good one that functions as designed. I recently got one ($5 out of pocket) and actually wear it.
That to me is the best kind.

You have my sympathy. My knee trouble goes back to age 14. I have had everything on my knees from Ace bandages to hard plaster casts. I’ve had physical therapy, ultrasound treatments, surgery, and even (shudder) a cortisone injection into the kneecap. As with so many other things, I’ve ended up pretty much managing it myself through trial and error when medical interventions proved ineffectual. (The surgery when I was 27 was necessary, and it helped, but the old joint has never been right since.)

The last time one knee went out, I went to Walgreen’s and bought one of those soft blue stretchy tubes with the cutout kneecap, and I used a cane to help reduce the stress. That seemed to work about as well as anything. After 4 or 5 months it settled down again.

I’ve heard that the Cho-Pat one is good.

The one I reference above is the DonJoy Reaction Brace
It works for me. My knee issue is simply over use from hiking, volleyball, racquetball, cycling, etc which I still do.