I was surprised when I first learned the etymology of "amateur", but now I frequently use it in this sense. Glad to see someone smarter than me has helped set the precedent. https://twitter.com/ArchieG1946/status/1254321366754627584

Chesterton uses amateur in its proper sense. See this description of his father:

"On the whole, I am glad that he was never a professional artist. It might have stood in his way of becoming an amateur. It might have spoilt his career — his private career.”