Cannot sign into beta.apple.com

For the last 2 years or so I have not been able to sign into beta.apple.com. I click either Sign In or Sign Up, fill out my login info and 2FA, and then I am redirected back to the beta.apple.com page with the Sign In and Sign Up buttons again. I do not get an error message. This happens on every device, every browser, and every network I attempt. I am also unable to log into the Feedback app on my iOS devices.

I am able to successfully log into all other Apple services, including appleid.apple.com and developer.apple.com.

For a while I created a separate Apple ID which allowed me to sign into beta.apple.com, but now that the betas are integrated into the Settings app in iOS, they do not appear for me because my iPhone is signed into my main Apple ID.

Judging from this existing thread from 2 years ago, many other people have been having this issue and have not had it resolved. Is there any way we can fix this?