This isn't a Minecraft bug, but a bug with the feedback website. It's no longer possible to log into it. When you click the Login link at the top right, it generates a URL and then just stops. It's not hung, it just stops working at a blank screen. This was in Chrome, where I always logged in previously.

So, I tried Edge, and there Microsoft tried to force me to use a different account (one of my outlook.com accounts), which wouldn't work so I quit trying.

Since there's no way to report the problem on the feedback site, I'm reporting it here in the hopes that someone can contact them and get the problem fixed.