how to not use them is editor dependent. but you absolutely don't have to use them. regular fonts are basically "use this image for 'a', this image for 'e'" e

how to not use them is editor dependent. but you absolutely don't have to use them. regular fonts are basically "use this image for 'a', this image for 'e'" etc. ligatures are extra data that says "if you find an 'a' next to an 'e', use this other image in place of the 'a' and 'e' images". but the non-ligature versions of characters are still in the font for use when there is no ligature sequence (just put a space in the middle of any ligature in your editor and you'll still see the independent characters rendered in the font).