Comment by KronisLV

Some additional ideas:

  - Kanban - Kanboard ( https://github.com/kanboard/kanboard )
  - Analytics - Matomo ( https://github.com/matomo-org/matomo )
  - Content Management System - Grav ( https://github.com/getgrav/grav )
  - Knowledge Base - BookStack ( https://github.com/BookStackApp/BookStack ) 
  - Browser - Firefox ( https://github.com/mozilla )
  - Image Manipulation ( https://github.com/GNOME/gimp )
  - Observability Platform - Zabbix ( https://github.com/zabbix/zabbix )
  - Password manager - KeePassX ( https://github.com/keepassx/keepassx )