Verify the claim first. (It's not true.)

Rupert Murdoch owns 21st Century Fox, which brought the magazine in 2015 for $725M.

Disney bought 21st Century Fox from Murdoch two years later.

His ownership was very brief. https://en.wikipedia.org/wiki/Acquisition_of_21st_Century_Fo...

No need to cancel a subscription over old news.

So the money raised by the sale of magazines now goes to research and exploration again?

The National Geographic Society still exists, yes, and makes money off the partnership with Disney. Their current programs are listed at https://www.nationalgeographic.org/projects/programs/.

Is there any proof it ever stopped?

If you're boycotting something based on false rumors you read on an Internet forum, I'm not sure how you buy anything.

Hey, I heard that Kim Jong-un bought out all the world's watermelon farms, so every time you buy a watermelon you're contributing to the oppression of North Koreans!

That's a lot of words to say: "the OP is incorrect". But I appreciate your concern.

And, so there is some factual outcome or use to this thread, I'd like to add that I'm looking forward to Murdoch rotting in actual, or metaphorical, hell.

You're welcome.

The OP isn't boycotting anything, he's signalling.