What to use instead of em-dash (U+2014), etc em-dash: — (U+2014) looks a lot like 一 (U+4E00) in many fonts.  What is typically used instead in Chinese print?  Or do they just rely on context?

What other punctuation alternatives should I learn?
I guess by "in print", you mean in (normal) computers, as you also mentioned Unicode code point.

We use 破折号 for this. And in computers, it is not one Unicode character, but two.

The symbol used is still U+2014, as I tested with my IME in Word. Two consecutive U+2014 form one 破折号 in Chinese. When Chinese fonts are applied, there usually no gap between the two U+2014 symbols, and it is two times longer than a normal character. (However, you might see a gap in between if non-Chinese fonts are used).

When Chinese fonts are used: To distinguish with 一 (one, U+4E00), double U+2014 is two times longer. And there is almost always a gap between two U+4E00 characters.

It might be a different story if specialized printing systems (computers), character sets, fonts, ... are used.