Peel citrus, separate segments, and carefully remove the thin skin and white pith from each segment. It is time-consuming and very tedious, but sometimes you need an activity that lets your mind wander while keeping your hands away from your phone. You can of course, peel the citrus, and cut cross-wise into round slices that look like bright colorful suns.
Arrange the citrus segments and avocado slices on a serving plate with high sides (to keep the citrus juices). Add sliced kumquats.
Drizzle citrus and avocado with olive oil and lemon juice. Scatter red onions, feta cheese, and chopped pistachios over the citrus and avocado. Sprinkle with ground black pepper and a little bit flaky sea salt (will depend on how salty the feta cheese and pistachios are).
Citrus segments by themselves, i.e. without olive oil and additional salad ingredients, can be kept in an air-tight container in the refrigerator for two days. Avocados will not last, but why wouldn't you just eat them all.