I agree no younger than 13.
Knowing my son, it wont be until highschool for us, at the earliest. A middle school boy showed my son how to look up naughty words on Spotify/the internet. So, big nope from me.
We do limited supervised access only for educational purposes. The internet is a tool, and my child dont need that in his pocket.
I/we have never felt social pressure to get him a phone. He's today 12. He makes friends everywhere he goes. Right now in this life stage I have a focus on teaching internet safety, how marketing works, and how to spot reputable/non reputable resources.