If my country decides to ban the ownership of general purpose computers for individual persons, they would order the customs service to stop import of any computer hardware that enabled general purpose computing. Now I would not be able to have any computer shipped to me from outside my country, so I could no longer buy from either of those vendors you linked.
Furthermore, it also would mean that I would not be able to bring any personal computers with me when I travel to other countries. I like to travel, and I like to bring my computers when I do.
Next, it would also be dangerous to try to buy computers locally within the borders of the country. The seller might be an informant of the police, or even a LEO doing a sting operation.
And then next you have to worry about the computers you already have. If you decide to keep the computers that you had since before, after it is made illegal to own them, you will have problems even if you keep them hidden and only use them at home. Other people know about your computers. Some of those people will definitely tip off the authorities about the fact that you are known to have computers.
People would take the CPUs out of other devices and use them. A consumer grade router has most of the hardware you need to make a general purpose computer.
https://frame.work/ and the https://mntre.com/ MNT Reform: Exist