That’s a very interesting resource!
Actually, the countries where I have been able to purchase anonymous SIM cards are in the list “As of 2021, the following countries do not have mandatory SIM card registration laws”. So, it appears like I just happen to have been lucky and I should not make this as such a general recommendation…
Funny, about Mexico it says:
Countries expected to implement mandatory SIM registration in 2022: Philippines, Mexico.
I can at least confirm that I was not asked for ID when buying SIM cards last year in Mexico.
I just looked it up and found the proposed law for Mexico on Wikipedia. It was struck down in 2022 as unconstitutional.
So, then, I really have no anecdotes to say that it is easy in places where it is formally illegal.
I am currently near Cologne in Germany. I placed one of these LycaMobile SIM cards from NL and it activated automatically. It does recognize that it is connected to the German network and roaming, and still activates data and assigns a phone number.
So, it seems to work fine