"you'll have to upload ID to watch porn"
Only if complying websites (yes, websites need to comply) think you're from the UK. Get a VPN and set it to any other country (that doesn't have age verification). Have no idea what a VPN is? Just download a browser with a free one built in (e.g. Brave) and Bob's your uncle.
Pornhub is compliant but some people seem to think PH is the only porn site on the internet. Guess what? There are hundreds of thousands of porn sites. Over 99% of them aren't going to give a damn about the UK's age verification (each site has to add a landing page for UK visitors). PH is blocked and no VPN set up? No prob just go back to Google and search (and end up on a lesser known and more dodgy porn site probably).
From a discussion I just saw it's also apparently easily fooled by using a stock image from image search of someone holding a driving licence.
Then we have the security and privacy risk. Everyone who is foolish enough to verify their ID is going on a porn user database. It's not a "if" this database will be leaked it will be a when.
The UK has been considering this idea since 2013, scrapped it in 2019 but then brought it back with the Online Harms Bill. It's the sort of law that looks good in paper but is a train wreck in reality.