NAA in Outlook Add-in: brk-multihub redirect URL rejected

[msgsergei]

I'm using nested app authentication (NAA) in my Outlook Add-in.
I have an app configured like 6 months ago with "brk-multihub://..." redirect url.

Today I was trying to add another 'brk-multihub' redirect URL, and I started getting the error:
"Must start with HTTPS or http://localhost/"

So it was working 6 months ago, and now I can't add a new url.
I'm wondering if something changed? I can't find any updates on this.