Office

Libre Office
Like : Microsoft Office

Offers Word Processing, Spreadsheets, Presentations and database/

Windows, Mac & Linux

https://www.libreoffice.org/

Internet/Comms

Video/Graphics

Gimp
Like : Adobe Photoshop

Fully featured image editing package. Suitable for editing photos and other images for web and print.

Windows, Mac & Linux

https://www.gimp.org/

Inkscape
Like : Adobe Illustrator

Vector Graphics package for creating logos, and images for print/cutting.

Windows, Mac & Linux

https://inkscape.org/

Shotcut
Like : Adobe Premiere

A video editing package allowing you to edit and add effects to your videos. 

Windows, Mac & Linux

https://shotcut.org/