Most forums and chat servers won't have to introduce age verification, because the content their users generate while participating in discussion doesn't need to be age-gated, and anything that would need to be (such as pornography) is off-topic and will be removed by moderators anyway.

This link may be of interest: https://www.mumsnet.com/talk/site_stuff/5383111-online-safet.... It's about how one of the UK's largest forums is complying with the OSA and why they are taking this approach.