HN user
Yes, such mods were actually quite popular. Here is one example: http://blog.tynemouthsoftware.co.uk/2020/03/a-zx-spectrum-wi... You can buy upgrade kits even today: https://www.retroleum.co.uk/spectrum-repairs-mods
Borland Turbo C++ (and Pascal as well) had great help documentation. Every function was thoroughly explained and there was a lot of examples. I learned C just by reading Turbo C++ help docs. I miss that time.
nand2tetris is free on https://www.nand2tetris.org/course The course is also available on Coursera where it also offers free option if you do evaluation yourself ("auditor" mode).
Not OP, but I can recommend Glider: https://github.com/Mosc/Glider It is a nice replacement of Materialistic.
And your wish is granted: https://github.com/swsnr/mdcat mdcat can render images in iTerm2, Kiitty or WezTerm It has a few quirks but great piece of software nonetheless.
Microsoft PowerToys also contain a new neat launcher called "PowerToys Run" which is similar to Launchy. It supports various plugins including Calculator. I like the feature that it shows up on the display where the mouse pointer is currently located so you don't have to jump between displays.
Looks like it is also possible to buy "punch limiting" harness. Here is an example search on Ali: https://www.aliexpress.com/w/wholesale-expander-boxing.html
There is also Dyson Sphere Program with similar reviews.
I think https://www.rtl-sdr.com/ would be a good place to start learning about SDR USB sticks. But beware -'this rabbit hole goes deep!
Maybe try k2pdfopt (https://www.willus.com/k2pdfopt/) It is a Windows/Linux application though.
Strange Parts YouTube channel offers some insights into Chinese electronics industry: https://www.youtube.com/channel/UCO8DQrSp5yEP937qNqTooOw
Actually, depending on your phone carrier, it might be possible to send SMS even to landline: https://www.theregister.co.uk/2004/08/05/bt_land_text/