I am running MediaWiki 1.37.2 along with BlueSpice 4.2.0-alpha.
I followed the instructions at Extension:BlueSpiceFoundation, except for the part where you add code to LocalSettings.php. Instead, I added wfLoadExtension( 'BlueSpiceFoundation' ); since the BlueSpiceFoundation.php file does not seem to exist anymore. This seems to toggle the extension on, as I can see it is active when viewing Special:Version.
I also followed the instructions to install the BlueSpiceReminder extension. I can also see that extension is active when viewing Special:Version.
I also have new links in my interface to view and add reminders. However, when I click them, nothing happens or no content loads on the page.
Is this a compatibility issue, or something else going on? Happy to provide additional details as needed.