Heat the olive oil in a large stockpot over medium heat.
Add the diced onion, carrots, and celery, sautéing for 5-7 minutes until the vegetables begin to soften.
Stir in the minced garlic, dried thyme, sea salt, and black pepper, cooking for 1 minute until fragrant.
Rinse the lentils and add them to the pot along with the whole chicken breast and chicken broth.
Bring the mixture to a boil, then immediately reduce the heat to low and cover with a lid.
Simmer for 25 to 30 minutes, or until the lentils are tender and the chicken is fully cooked.
Remove the chicken breast from the pot, shred it using two forks, and return the shredded meat to the soup.
Stir in the chopped kale and lemon juice, simmering for an additional 2 minutes until the kale is wilted and bright green.
Adjust seasoning if necessary and serve warm.