The Wikipedia page implies that all the designated "Category 1" websites will now either have to collect ID from their users worldwide, or remove any presence in the UK.

Edit: there's a list of the Category 1 services at

https://www.ofcom.org.uk/online-safety/illegal-and-harmful-c...

I.e., Facebook, Instagram, Pinterest, Quora, Reddit, Roblox, Snapchat, TikTok, Whatsapp, X, YouTube.

Plus others at the Category 2A or 2B levels.

Edit: well, it says they are "Providing user identity verification options." Unclear to me when they are supposed to get users to verify identity.