Ah yes, Jacob Collier. What I like is that he suggests an exercise that he used to practice microtonal singing: see how many intermediate pitches you can sing between two notes (could be a half step apart or you could start with a wider interval) and try to increase that number.
Of course if you sing Indian classical music (or several other non-Western musical traditions) then you will learn to sing quarter tones.
Someone shared this recently: https://www.youtube.com/watch?v=XwRSS7jeo5s I struggle to conceive being able to hear the difference, but _singing_ it entirely blows my mind