Steam Account - Can't access

Depends. A similar thing happened to me and I was able to verify my account by sending Steam support a photo of a Steam key I had activated on that account. This was literally over ten years ago though, so don't know if that's still an option. Either way, contact support.

Think you have to go through the Support page, if it's even possible.

Don't suppose you linked a phone number to your account?

Have you gone through the steps on the page I linked?