Does anybody know more about Atlas Privacy, the company behind this new site? According to PitchBook they were founded in 2021, are privately owned, but backed by venture capital.
Edit: Brian Krebs uses their research as a source sometimes.
There is also breachdirectory.org, which is more useful as it displays a part of the actual password leaked, so you actually know if your passwords were compromised.
Can’t access website with a VPN 
(edit: seems to be working now)
Does it support k-anonymity like HIBP does?
you mean this k-anonymity - Wikipedia ?
Yes, it does
Delaware-based Atlas Data Privacy Corp. helps its users remove their personal information from the clutches of consumer data brokers, and from people-search services online. Backed by millions of dollars in litigation financing, Atlas so far this year has sued 151 consumer data brokers on behalf of a class that includes more than 20,000 New Jersey law enforcement officers who are signed up for Atlas services.
Atlas alleges all of these data brokers have ignored repeated warnings that they are violating Daniel’s Law, a New Jersey statute allowing law enforcement, government personnel, judges and their families to have their information completely removed from commercial data brokers. Daniel’s Law was passed in 2020 after the death of 20-year-old Daniel Anderl, who was killed in a violent attack targeting a federal judge — his mother.
from The Global Surveillance Free-for-All in Mobile Ad Data – Krebs on Security