My DD age 9.5 has had a phone for years, as it was cheaper to give her an old iPhone than get her a camera. Last year we put wifi on her phone so she can Facetime grandparents and cousins.
During lockdown, we have set her up with Skype too and she chats with her friends 7 days a week in group calls often whilst playing Roblox with them. It is the highlight of her day, and to be honest mine too, as it is lovely listening to them chatter and giggle and play. We have set up limits on apps so she has to ask permission to use more time, and her devices turn off at night and won't work until morning.
Do I regret accelerating her phone use by a few years? Yes, sure. But far less than I would have regretted isolating her from her friends from March to August. Life is full of tough choices.
Just a month ago my OH decided to put a cheap SIM in her phone. The purpose for now is not to make calls, it is for emergency use and so we can track her - we have recently allowed her to cycle to the park on her own but we want her used to the idea that we always need to know where she is.
PS my DD is a very, very outdoorsy kid, and yet still would spend all day on screens if I did not encourage her to turn them off! Screen time is highly addictive. Never too young to teach them how to behave responsibly and how to turn the screen off and engage in real life.