It's an American obsession.
UnityDevice
It's a size of paper with an aspect ratio of 1:√2, and the short edge that is 21cm long. The long edge will then be 21√2 = 29.7cm. The aspect ratio has the interesting property that it can be halved and doubled while remaining constant.
This has been your ISO fact of the day.
You can start here: https://hackaday.io/project/176931-hp-printer-cartridge-control-module/details
HP printers are conceptually quite simple devices, the printer just moves the cartridge and the paper. The cartridge does all the actual printing. So you reverse engineer the pinout on the cartridge and you can make your 3d printer do normal printing. That's also how those little handheld cube printers work.
I love how the complaint makes even less sense when you look at the KDE mega announcement from yesterday. The third thing listed is a new wallpaper.
Love KDE, but they have some really annoying users.
It actually seems common for less developed countries to have better internet than the more developed ones. Germans always complain about their internet, for example. I believe the reason is simply that your country laid down lines relatively recently, so they're compatible with high speed internet, while Germany laid down their lines 30 years ago, so they're fairly shitty in comparison. It tends to be a lot harder to convince governments or bosses to replace something that seems to work fine, and it can be costlier too.
set -euo pipefail
at the top of every script makes stuff a lot safer. Explanation here.