Apple - How do you type a character with its ASCII code?

Add Unicode Hex Input as your Keyboard. Hold the option key while typing.

It's there for me in Character Viewer (Emoji & Symbols, expanded version). It doesn't have a glyph, but if you double click it should be inserted.

Note that you may have to go to the gear wheel at top left and select Customize to add the Unicode category. The Unicode category is under Code Tables.

If you like to use the terminal, you can do this:

printf "\x0c" | pbcopy

This pipes a single formfeed character to the pbcopy, which stores it in the system clipboard. You may then paste it into whatever app you need.