Sonarr, Radarr, Lidarr, Readarr, and Prowlarr.

Infinitime, for my PineTime.

Yggdrasil, an IPv6 end to end encrypted networking proof of concept. There's something about it that I find so innovative that I want it to succeed so badly !

Pihole, Kubernetes, ffmpeg, VLC, pretty much we are so technologically advanced because there is so much free and open source software. If it wasn't for it we would be ages behind technologically.

mpv.io !
I discovered it before covid, and it is really lightweight and customizable. So many plug-ins, and they're so simple to create.
I was usually having issues with VLC or settings that he didn't have. No issues with mpv, so far.

Blender

Godot game engine without a doubt.

I couldn't get by without AutoHotkey and AltSnap. Especially having extra buttons on my mouse, there's so many custom shortcuts, commands, controls, etc. that I couldn't make without them. AltSnap also has a built-in borderless windowed button that works better with games than some apps I have used that are explicitly for that purpose. I have shortcuts for changing volume, switching windows, toggling always-on-top, and even making windows transparent all from the mouse.

Firefox, GNU Linux, VLC, GIMP, Krita, Blender (even if I didn't used it that much), Lemmy of course with it's different FOSS clients

The Linux Kernel and operating system in general. It is simultaneously my favorite and I hate that it killed my prior favorite, the SGI Irix operating system. I was there at the beginning, from kernel 1.1 through today. I remember telling regional directors at silicon graphics that Linux was the future and them disparaging that opinion.

archlinux firefox thunderbird emacs

OsmAnd

Emacs, tor, mpv, KDE, f-droid, python, qemu

I'unno. Don't really think about it that hard.

I guess firefox, since it gives me ~~porn~~ access to websites.

OBS is my one of my favorite softwares in general, let alone open source

Subsurface

Its dive planning and dive logging software. It's also the only software I'm aware of that can actually pull the data from my dive computer, which uses some crappy proprietary cable and software. The fact that subsurface exists and is automatically in Linux repositories is what finally allowed me wipe out my aging and barely functioning computer, and revive it with Linux.

KDE Plasma desktop

Linux, MPV, Proton, bash, Newpipe

youtube-dl

Firefox, Libreoffice, and Bitwarden (I would include Zotero, but idk if it's open source)

Bitwarden & Jellyfin

Wine, despite the headache that is fiddling with its configurations for specific older games to work.

Dolphin Emulator always amazes me in how perfect of an emulator it is.

Hyprland So much fun

Debian

Gotta go with python here, though vim would be a close second.

Since most of what I would have said has already be mentioned I will just go with almost anything under the umbrella of the KDE organization.

As in the Plasma desktop environment and the whole application suite. Includes programs like Krita, Kdenlive and KDE Connect, plus the whole range of "standard" desktop applications like terminal, file manager, document viewers, etc. pp.

And the DE itself is just adorably hackable. Want to replace the Kwin window manager with i3? Sure it's possible, here you go: https://userbase.kde.org/Tutorials/Using_Other_Window_Managers_with_Plasma

Android and Linux

Freecad. It's a little rough to use compared to professional cad products I've used but it can really do a lot. In a lot of ways it feels less constrained than some of the stuff I've used too