Older versions of IE have been dropped. And Edge is still their recommending browsing experience and the only one likely to receive enhancements (both will continue to receive security fixes).
Key Dates:
- Internet Explorer 9: EOL January 12, 2016
- Internet Explorer 10: EOL January 31, 2020
- Internet Explorer 11: EOL Unknown/Unannounced
IE11's EOL date is currently unknown. It would be at minimum 2025 based on Windows 10's current extended support date (but each Windows 10 feature release with IE11 pushes that date back).
Imagine TLS 1.4, or some other change that will occur that will completely break IE11.
Instead, Microsoft will ship Edge with Chromium (even on Windows 7) and say "use that instead" and will eventually remove IE altogether.
The PR specifically says "* Remove IE (but not Edge)" and to update docs containing IE references.
> IE itself is being "dropped" as well, so long term support commitment for new products does not make sense.
Also if you need to support IE you're probably not in the position of converting your application to BootStrap v5.
Microsoft is telling everyone to not use IE11. They are not adding features to IE11, or fixing (non-security) bugs. While it is the only browser shipped with LTSB, Microsoft's position is that no one should be using LTSB on general-purpose machines anyway. (Mind you, LTSB works and is wonderful, but Microsoft would prefer you don't know that.)