Also add a banner at the top telling people they need to use their other browser for the page.
What business are you in where 8% are still on IE11?
You can try the polyfill approach. This is generally not recommended as it wastes bandwidth. But since your customers have bandwidth you could go with polyfills. Or just stay stuck in the past with a niche of writing IE11 compatible stuff. That could be career limiting, IE11 is getting as irrelevant as 8.3 FAT filenames.
https://en.wikipedia.org/wiki/Microsoft_Edge
Edge is supposedly an option even back to Windows 7, though I don't believe it's a required security update. I haven't used a Windows 7 system in long enough that I'm not sure.
At this point it is reasonable to tell people they NEED to install a more modern (and more security up to date!) web browser, be it Google Chrome, Microsoft Edge, or Mozilla Firefox.
Many government and healthcare organizations STILL using Internet Exploder, presumably until its 2025 end of life:-(
As far as I know, Microsoft plans to keep IE11 around as long as Windows exists.
Oh you sweet summer child...