I have never used sodium citrate in mac and cheese because I could find it only in large quantities, for around $20.
Today an Emmymade video popped up on FB. She made 1.5 cups of coarsely grated cheddar into a smooth sauce using a knob of unsalted butter and two Alka Seltzer tablets dissolved in water, nuking in spurts.
I was unable to link it here but you can find the details on her FB page.
Hope to try this once it’s no longer too hot to think about cooking…maybe in 3 months?