Moodle (https://moodle.org/)
NextCloud (https://nextcloud.com/de/)
CryptPad (https://cryptpad.fr/)
LernTools (https://codeberg.org/lerntools/)
MintApps (https://codeberg.org/tk100/MintApps/)
Wiki (https://www.mediawiki.org/ + https://www.semantic-mediawiki.org/)