I would encourage newer books and classes to introduce keywords as they become necessary. There's no need to spam students with a bunch of words that have no place in a relevant class. For example, I'd like to see reinterpret_cast, const_cast, and union no longer show up in introductory material. Not mentioning consteval and co there is also a good idea.

When I teach beginners about what they can use as a legal identifier, I simplify it to "use only letters, numbers, and underscores, don't start with a number or underscore, oh, and don't use any of these", and then show the list of keywords and other reserved words. (Granted, this does lead some inquisitive people to ask "what does this do? what does that do?". I'm forced to brush them off so I can move on by saying something to the tune of "if you don't know what it does, you probably don't need it" or "when you need it, then you'll know what it does"... but that's something I have to do a lot when teaching C++ anyway.)

Are there any other options for telling beginners what they can use for their variable/function/class/whatever names? Without showing them the list of keywords, how would they know they can't name something "union" or "register" or "default"?