My older son had instagram at 14 when he was doing a photography courses that used it as part of showing their work, though hasn't used it in a while, and switched mostly to Discord. Him getting instagram at 14 lead to a rule that at 14 they could pick one social media, but it ended up with my second that her friends found this idea fascinating and basically tried to sway her choice by saying what was wrong with the different sites & apps so she ended up not picking any for months as her friends made them all sound like awful, glitchy time sucks. She got with Discord around the same time as her brother so we could do a family server.
Getting Discord does comes with regular chats about scams and issues going through there. At 14 year old, it's only the family server and clubs they attend in person - my current 14 year old has the school D&D club. The ones 16+ have other servers.
They also use youtube, but don't make any content on it.
My oldest (now 19) is on a few hobby webforums that work much like social media, and last year got Whatsapp for work. I was expecting my 17 year old to follow suit when she started her apprenticeship, but her workplace uses email for everything - something about it being easier to put virus protection and similar on there - so she's got her email app on her phone going off instead.
Oh, and my kids have Family Link on their phones, and all but the oldest have it so any apps require an adult to approve. The 17 and 14 year old can take it off any time, but the 17 year old likes us to check for scams after my oldest had an issue with that and the 14 year old is just fairly content as she mostly just wants rhythm games on her phone.