We're taking it for granted that people do not want to be tracked on the internet, and certainly don't want everyone to have to verify themselves on every site they use. I personally spent ages of time campaigning against the legislation (and lost) - e.g.
https://matrix.org/blog/2021/05/19/how-the-uk-s-online-safet... and
https://element.io/blog/the-online-safety-bill-an-attack-on-... etc.
The difference with Discord is that Matrix is a protocol, not a service. It's made up of thousands of servers run by different people in different countries. Public instances may choose to verify users in affected countries to abide by the law; others may choose to run a private instance instead.