The link to check if you were affected is reportedly legit, but it couldn't possibly have been done more poorly by Equifax.
Instead of setting up a sub-domain under Equifax, they setup a site with a totally phishy looking name that is a non-Equifax domain signed with a CloudFlare DV SSL cert with an expired CRL.
The results it gives are then sort of confusing, tells you to come back to be enrolled in credit monitoring if you were affected instead of allowing you to enroll immediately (my guess is they're hoping you forget and then don't enroll), or they try to sucker you into signing up for credit monitoring even if you weren't affected.
And the credit monitoring is reportedly only for a year. That is some serious garbage. If you collect every piece of identifying information you can on everyone without their consent, and use that information to directly affect their financial life, and allow that info to be stolen, you should be forced to provide credit monitoring for a lifetime for everyone affected.
Better yet, the federal government should make it illegal to use SSNs as identifiers and authenticators outside of federal government use.