Group-Office.

Dutch open-source groupware with email, calendar, file sharing, and CRM modules

Facts

Ashampoo Office
German office suite with word processing, spreadsheets and presentations, Microsoft format compatible
DE · commercial
↗
CryptPad
French end-to-end encrypted collaborative office suite with documents, sheets, and presentations
FR · open-source
↗
EGroupware
German open-source groupware suite with CRM, project management, and collaboration tools
DE · open-source
↗
Etherpad
Open-source real-time collaborative text editor, widely deployed across European institutions
DE · open-source
↗
Grist
Open-source modern spreadsheet platform combining the power of databases with familiar spreadsheets
FR · open-source
↗
grommunio
Austrian open-source groupware and office suite as a Microsoft Exchange and Office alternative
AT · open-source
↗
Horde
Open-source groupware framework providing webmail, calendar, and notes used by European providers
DE · open-source
↗
LibreOffice
Free open-source office suite maintained by The Document Foundation in Germany
DE · open-source
↗