The previous bug submission page has been shut down in favor of a new Issues & Bug Reporting section on the official Unreal Engine forums. Once a post there hits 5 upvotes, a ticket will be created in Epic's system. This new process will allow users to track the status of bug reports, continue discussing them in context, and provide additional information if needed.

It's unclear if this new system connects to the existing issue tracker or if that will be shut down as well. I'll update this post if I can find out.