Inkscape is really good and I prefer it over Adobe Illustrator. It’s a bit worse in some regards but its really stable and does everything very reliably and can be molded into svg production machine.

Kdenlive is the best simple video editor out there. Sure other editors are better but kdenlive really hits that sweet spot of being simple but powerful.

Digikam is the best photo management suite I know off. Everything else seems to be missing one thing or another and Digikam just does everything and does it pretty well.

Ansel (fork of Darktable) is often better than Adobe Lightroom for casual photography as it comes with very strong opinionated defaults. I generall just follow the default pipeline and have amazing shots. Light room could probably get me a bit further but Ansels hits the sweet spot between too basic and too clunky.

Then as a developer foss libraries are basically uncontested to the point where proprietary libraries and programming languages are basically do not exist anymore.