Uh… what is happening in the UK?
UK Online Safety Act.
As in, every Brit who wants to use any kind of online service must prove that they're 18+ IRL. Not just by clicking a checkbox. That isn't sufficient. But by sending a copy of their ID or passport to the admins.
Option #1: As an admin, demand all your UK users send in rock-solid proof that they're 18+ IRL and ban those who don't.
Option #2: As an admin, save yourself the hassle and IP-block the UK.
Option #3: As an admin, save yourself all this hassle, don't do jack $#!§ and risk the UK declaring your service illegal by UK laws and blocking both your domain and your IPs.
Lemmy.zip chose option #2.