I'll list a few of my regularly-used tools, both CLI and GUI.
CLI:
ncdu: An interactive TUI variant ofdu, for tracing disk usage across targeted directories.podman: An alternative runtime to Docker that is arguably just better at this point. Can handle rootless containers with ease, works with SELinux, can handle Docker compose files with add-on toolpodman-compose, can automatically update containers intelligently, can integrate well with SystemD, and more.mtr: Another network tool. Effectively traces network routes to a given IP. Great for diagnosing faults in latency or major packet loss.ffmpeg: A very complicated, but powerful tool for converting, manipulating video and audio files in all sorts of ways. FFMpeg can essentially be the answer to any 'do X to Y file' question.
GUI:
- Kdenlive: A powerful video editor developed by KDE. For free and open source, it is impressive how little you can't do when editing videos with this tool. A bit buggy at times, but has gotten significantly more reliable over years.
- Handbrake: A FFMpeg frontend that allows for mass transcodes of video files based on created profiles. Great for archiving, finalizing videos down for web upload, or just converting content to a more efficient format. Specializes in lossy/destructive operations.
- LosslessCut: A FFMpeg frontend that allows for trimming videos, stripping and/or exporting tracks from videos, editing mkv metadata, editing video chapters, and any other lossless/non-destructive operations that can be done on video files.
- Subtitle Composer: An outright semi-professional-grade subtitle editor developed by KDE. Supports and can convert between pretty much any subtitle format you might encounter. Great for creating, editing, timing, and translating subtitles for videos.
- KeepassXC: My password manager of choice. Has browser autofill integration, though requires some holepunch work to function with Flatpak browsers. Explicitly is based on local files. Does not rely on cloud providers.
- Limo, R2Modman: Native mod-managers that allow for modding various Steam games (native and Proton) on Linux.
- Blender: A powerful 3D editor. Capable of hard and soft 3D modeling, character rigging, animation, material creation and UV mapping, compositing and rendering. Pretty much an all-in-one tool for 3D art and design.
- FreeCAD: A somewhat daunting, but functional 3D CAD software. Has received a lot of recent (~3 years) patches to improve on a lot of long-standing pain points in the software.