Planck’s career until 1900 https://www.mpg.de/19252773/plancks-career-until-1900
When Max Planck presented his radiation law in 1900, the 43-year-old was already an established authority in physics and a highly-regarded member of the scientific community. It was his work on thermodynamics in particular that had made him famous.
His professor in Munich was Philipp von Jolly, but lectures by Hermann von Helmholtz