What's the best tool for screen sharing, collaboration and pair programming?

Screenhero is not accepting new users anymore without an invite after being acquired by Slack. I'm looking for something similar to Screenhero but with support for all operating systems.
Michael LeeMaker of things for humans · Written
I know you mentioned all OSes, but if you're both on macOS and in a pinch, Messages has a great little feature where you can share your screen even allow access so the other individual can control the cursor and i/o. I've done this in quick code reviews.
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