I know newspaper columnists. They aren’t paid by anyone except their publisher. If there was money to be made on the side as the mouthpiece of private interests, a lot more people would be going into journalism rather than leaving the profession in droves.
As for columnists I enjoy:
Robyn Urbach - Globe and Mail (paywalled). Mostly politics. Manages to have personality and a bit of bite without descending into snark.
https://www.theglobeandmail.com/authors/robyn-urback/
Conor Friedersdorf - the Atlantic (paywalled, 3 free articles a month). Politics and culture. Big picture issues from a liberal perspective.
https://www.theatlantic.com/author/conor-friedersdorf/
Yascha Mounk - the Atlantic (paywalled, 3 free articles a month). International politics and global trends. Looks beyond the minutia of day-to-day politics.
https://www.theatlantic.com/author/yascha-mounk/
Caitlin Flanagan - the Atlantic (paywalled, 3 free articles a month). Social issues and culture. Insightful and often funny.
https://www.theatlantic.com/author/caitlin-flanagan/
David Mitchell - the Guardian (free). Culture and humour. One of the funniest people alive (ie “are we the baddies?”)
https://www.theguardian.com/profile/davidmitchell
Most major newspapers and magazines have returned to a subscription model because Facebook took their ad revenue lunch.
Interestingly, the Economist not only doesn’t have opinion columnists, it doesn’t even have bylines. One of the most prestigious english-language newspapers/magazines and its writers are pretty much anonymous.