Many/most microcontroller boards have analog-to-digital converters built into them, it is very convenient. E.g. it is the case for the Raspberry Pi Pico.
The model is extremely simple, but has been proven to be able to solve all the problems that any reasonable computer model can solve, thus its adoption as the "default model".
The smallest known Turing machine that cannot be proven to halt or not as of 2019 is 7,918-states: www.scottaaronson.com/blog/?p=2725. Shtetl-Optimized by Scott Aaronson is just the best website.
A bunch of non-reasonable-looking computers have also been proven to be Turing complete for fun, e.g. Magic: The Gathering.
This is the lowest level of abstraction computer, at which the basic gates and power are described.
They may have nice looking save the world charity campaigns, but once you get even close to affecting their revenue stream, the axe falls. The charity is only a publicity stunt to reduce wages.
Some level of government intervention is needed to control investor's greed.
It is just a question of business model: some business models are eviler than others. Making people pay for operating systems being possible the most evil of all.
One thing must be said however. You can learn a lot by working in a good company, because it ends up putting you in contact with practical real problems that you wouldn't otherwise see by just doing your own random low-tech startup. This is especially valuable if said company is also enlightened enough to use and contribute back to open source software, thus improving the world and paying back the moral debt of using other people's work for free.
Another important point to consider is who in the company is evil. In a sane tech company, the lowly engineers are going to be non-evil. And then the more you go up the management chain, the more aligned you have to be with investors, and thus the more and more evil you get. HR is just evil from the bottom though, it's just the nature of their job.
Which boundary conditions lead to existence and uniqueness of a second order PDE by 
Ciro Santilli 37 Updated 2025-07-16
Ciro Santilli 37 Updated 2025-07-16www.cns.gatech.edu/~predrag/courses/PHYS-6124-12/StGoChap6.pdf 6.1 "Classification of PDE's" clarifies which boundary conditions are needed for existence and uniqueness of each type of second order of PDE:
Ciro Santilli is very fond of this result: the beauty of mathematics.
How can so much complexity come out from so few rules?
How can the proof be so long (thousands of papers)?? Surprise!!
And to top if all off, the awesomely named monster group could have a relationship with string theory via the monstrous moonshine?
The classification contains:
- cyclic groups: infinitely many, one for each prime order. Non-prime orders are not simple. These are the only Abelian ones.
- alternating groups of order 4 or greater: infinitely many
- groups of Lie type: a contains several infinite families
- sporadic groups: 26 or 27 of them depending on definitions
Simple Groups - Abstract Algebra by Socratica (2018)
Source. Good quick overview. There are unlisted articles, also show them or only show them.