My daily driver machine is refurbished Thinkpad x260 running Manjaro (with i3). Raspberry Pies are also great tools that I hold very dear (in fact, this website is powered by one!) and I would wholeheartedly recommend getting one if there's interest in GNU/Linux, running a server, etc.

For text and code editing, I use (neo)vim. I'll do code in Python, C, and Scheme.

For mathematics, I cannot stress the greatness of SageMath.

mpd is a very complete tool for what I need in terms of music. For a front-end, I'll have ncmpcpp.

ffmpeg is an incredible tool for everything related to video manipulation, and VLC is very reliable at reproducing anything I throw at it.

I, uhh, I tend to hoard programming tutorials and resources that are somehow recommended or endorsed by Hacker News communities at large; and of course I will never go through all of it, but in case it is useful for anyone, behold my programming resources dump 📦.