Bootstrap 5 dropped the support for Internet Explorer and mean it seriously. There is absolutely no support for it anymore.
But there are still many areas in which Internet Explorer is strongly represented. Doctors, craftsmen, lawyers etc., wherever older or non-technical users can be. If you need IE Support, use v4.bootscore.me, it is still good.
If the page is browsed with Internet Explorer, an alert is displayed below the navbar. Check this site here in Internet Explorer emulator.
This is done by a pluggable function in /inc/template-tags.php and can be translated.
If you do not want to display the alert, open header.php in child-theme and scroll to the bottom. There you will find:
<?php bootscore_ie_alert(); ?>