Lettuce actually grows pretty easily.

Now you aren't going to trivially have enough to be a staple of your diet or anything, but if lettuce at the store is a problem, you could at least have a few leaves to add some to a few dishes while the issue is worked in the supply chain.

My kid just has a single lettuce plant and pulls a few leaves off to eat with something once in a while. It doesn't need much active care or anything.

At one point my kid had an indoor hydroponic garden going that offered up a bit more vegetation to eat, but keeping that thing maintained was a hassle.