A useful utility on the Mac is the Unicode Hex keyboard which allows you to press Option plus any four digit Unicode code to get that character.
For instance, if you need to enter the rarely seen archaic Roman numeral symbol for 5,000 (ↁ), you could look up its Unicode character number (U+2181), then activate this keyboard then type Option+2181 and generate the code (assuming the correct font is loaded).
But a lot of ancient scripts are in Plane 1, meaning they have Unicode values with five digits (i.e. U+10000 or higher). In Unicode world, adding the fifth digit means that some processes go slightly awry, and the Unicode Hex keyboard is one of them. Suppose I want to input Phonecian character Alf (Aleph) (