Mastodon

Not as far as I know. But you can check #journalism tag so find some people.
There are also some instances that a lot of them use, like:
https://federated.press
https://journa.host
https://newsie.social (more general one, but has some journalists)

Good question. :-)

It might work, e.g. on a v4.2 instance (with Ice Cubes or Mona). ;-)

Example

(For some reason, the same search doesn’t work with Ivory.)