He is going to have to convince the MO Dept of Revenue that he has been a resident of Florida since 2021. As a resident of Florida, he has no tax obligation to MO as long as he has no MO-source income.
At the very least, he should obtain a Florida State ID card in lieu of a drivers' license. See this:
https://www.flhsmv.gov/new-resident/
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
