I've taught programming to beginners, both children and adults, and lua is the worst of the languages I've done it with. It's an amazing technical accomplishment, and CS students should study its implementation. But for actual beginners its "focus on fundamental concepts" and flexibility are liabilities.

The main struggle people have learning to code is getting over the initial frustration hurdle where they can't actually accomplish anything yet. What they have to get them through this is excitement about their actual goals. With lua you burn too much goodwill and beginner spark on debugging string manipulation functions that don't seem important to the actual interest or goal that brought them to programming. Or figuring out how to use luarocks so you can make http requests, or regex, or whatever.

> 1-based indexing could cause beginners to get confused when they move to another language.

This is so far from the problems that beginners actually have. You should teach some programming, it's a really fascinating experience that will mess with your intuitions about how people learn this skill, and what's hard about it.