Graphics / Photography / Video
Gimp http://www.gimp.org
Gimp – vs – Photoshop https://expertphotography.com/gimp-vs-photoshop/
Rawtherapee https://www.rawtherapee.com
like Camera RAW image converter and processing software
Like Photoshop-CS
Darktable http://www.darktable.org/
like Adobe lightroom
Krita https://krita.org/
like Corel Painter Adobe Photoshop
Inkscape https://inkscape.org
like: Adobe Illustrator; CorelDraw; Affinity Designer
Blender http://www.blender.org/
like Maya
Scribus https://www.scribus.net
like Quarkxpress; InDesign MS Publisher
Kdenlive https://kdenlive.org/
like Adobe Premiere Pro
OpenShot https://www.openshot.org
like Simple Video editing software
Handbrake https://handbrake.fr/
like video ripper and transcoder software
Music Studio Software
LMMS http://lmms.io/
Rosegarden https://www.rosegardenmusic.com/
Audacity https://www.audacityteam.org/
Frescobaldi http://www.frescobaldi.org/
MusicBrainz Picard https://picard.musicbrainz.org
Clementine http://www.clementine-player.org/
Office / Work / Science Education
WPS Office https://www.wps.com/en-US/
like MS Office
Liber Office http://www.libreoffice.org
like MS Office
Dia https://wiki.gnome.org/Apps/Dia/
like UML editor Ckt Diagram Ms Visio
Accounting / Book Keeping
GnuCash https://gnucash.org/ like quick books
Investing-Money Mgt
Portfolio Performance https://www.portfolio-performance.info/en/
Genetics
Biogenesis http://biogenesis.sourceforge.net/
Ugene https://ugene.unipro.ru