Dietary sources of selenium include organ meats, seafood, eggs, dairy, nuts, and cruciferous vegetables.

Study: Associations between food group intake and serum levels of selenium and other essential and toxic trace elements in adults

This study found that people who ate more fish, dairy, and nuts had higher levels of selenium in their blood, which means those foods are good sources of selenium—just like the claim says.

Study: Selenium intake, food sources, and associated factors in Brazilian Longitudinal Study of Adult Health (ELSA-Brasil): a cross-sectional study

This study found that nuts and fish are big sources of selenium in people’s diets, which matches what the claim says. It also found meat is a major source, which includes organ meats, so the claim is backed up.

Study: Selenium Bioaccessibility and Bioavailability in Se-Enriched Food Supplements

This study didn't look at the foods listed in the claim, but it did check if selenium from yeast (a natural source) can be absorbed by the body—and it can. So it doesn't contradict the claim that selenium comes from foods like nuts and seafood.