How do I update Teamviewer (free) on an Apple?

I've used TeamViewer to help my mother, who is 90 next year, with her iMac. I'm on v15.4.5 (on my laptop as I am on holiday at the moment) and she is on a slightly older version of 15. Neither of us can update. (1) is the free version of TeamViewer still available? (2) How do I update it?

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