paracetamol F-strings are a relatively recent addition to Python
Thanks for solving that mystery!
Solus' python3 is 3.6.9, but it also has 2.7.16 installed. I'm sure that Sublime chose that one, and the syntax error(s) make perfect sense to me now. The book I'm studying uses F-strings throughout to display the results of its examples, which is why nothing seemed to work for me. It's good to know why. VScode apparently chose python3 for a default instead, which explains why everything just worked there.
That said, I'm still partial to Visual Studio. Like I said, it seems like an old friend. It's good to not have to learn a new IDE at the same time I'm learning a new language. I'm sure there's probably a way to change Sublime's default, but I'll still stick with VScode. I understand the value of having Python 2 installed, in order to run older code, but I don't see any advantage to learning version 2 to write new code.
So, a frustrating mystery solved, I learned something that I'll never forget, and I found my ideal Python IDE, even if it was by accident. This has been a good experience. Thanks for your help with it.