I didn't get anything similar from them, and there's no notice on their site.
Are you sure it's not a scam? Did you follow any links in the mail?
Edit - they do say that security keys are preferred over authenticator apps. But there's no notice, I didn't receive a mail, and there's no obvious reason they should know which authenticator you're using anyway.
It's weird. I didn't click any links, and I googled for news instead. And I found a bunch of stories, but I just noticed all the stories are from 3-4 years ago.
Hippy just linked to an article on their website which says they support GA and Duo, which is what the email said I should move to.
I didn't get anything similar from them, and there's no notice on their site.
Are you sure it's not a scam? Did you follow any links in the mail?
Edit - they do say that security keys are preferred over authenticator apps. But there's no notice, I didn't receive a mail, and there's no obvious reason they should know which authenticator you're using anyway.