I inherited this project last year and did an audit. There are a lot of issues. Instead of spending time to fix/update the project and bring it back into a maintained state, we're shutting it down.

There isn't another service like this one. However, I also maintain a Firefox extension called rob-bugson that does what github-bugzilla-pr-linker does and some other things, too:

https://addons.mozilla.org/en-US/firefox/addon/rob-bugson/

Thank you for your years of github-bugzilla-pr-linker usage!