The others have been mentioned. Not quite daily but I'll occasionally get paid to do CFD simulations.

FreeCAD, salome, openFOAM, paraview.

Programming, writing, notes, email… and basically a whole lot of what I use computers for is done with emacs.

Session

Librera (pdf reader and other formats), tuta mail (private mail), feeder (RSS reader), iceraven (Firefox fork), saver tuner (battery management), aurora store (replacement of play store), breezy-weather (for checking the weather), openBoard (Foss keyboard with spell correction)

Nmap, Wireshark, zenmap at work.

1. Firefox, nuff said.
2. Organic Maps on my phone. I prioritize it for the privacy.
3. Jerboa for Lemmy
4. Ubuntu Linux, partially due to needing to run some kind of Linux for a class. Most people went with WSL, I chose to dual boot.

tinybit
tor
droidfs
librera
octodroid
rosy crow
trebleshot
Trackercontrol

#android

I don't have a clue if anyone has mentioned it, but I use the non-root version of NetGuard to make sure some apps on my phone don't have wifi or mobile data access.

I also don't know if this was mentioned by someone else, but for one of my college courses, we are using thonny for python programming.

Define use? Anyone using the Internet relies on a lot of FOSS, even if we just consider webservers kn the www.

Like others, the list of non foss is shorter for me.