It’s not necessary to see the problems though

It's not clear that you will need an account to see the problems. Logged in with my account and it's exactly the same page. It's not Dec 1st everywhere yet, so they might open up for everyone when they do open them up.

This also has a paid account and a business account.

And if you have a paid account, you get extra time to complete the challenge!

Somehow, SadServers seems to have entirely missed the concept of a "puzzle".