An alternative is to use polyfill-fastly.net, generously provided by Fastly (@devs) to help migrate to another more maintained solution.
It has been set up by the original project author (now working at Fastly), runs the code that was running previously on the main domain, and have an amazing track record at supporting OSS projects.
Their announcement with more details here: https://community.fastly.com/t/new-options-for-polyfill-io-users/2540