On Macs, Courier (but not Courier New) can do it, though not by default.
(Open up TextEdit, enable Rich Text, select Courier, type "ff", highlight it, go to Font > Ligatures > Use All. The "ff" will now take up the width of a single character.)
I've run into a bug where certain styles of Courier Prime turns into ligatures in Google Docs. (Long story short, whether or not ligatures get enabled is a complex interplay between the OS, font, browser, and application, and not every layer always does it right.)
I'm not really sure why font designers even bother creating them in monospace in the first place though, I can't imagine any valid use for them. The only thing I can imagine is if a badly written application forces a ligature character, at least the end result will be readable rather than an empty box or something.
(Open up TextEdit, enable Rich Text, select Courier, type "ff", highlight it, go to Font > Ligatures > Use All. The "ff" will now take up the width of a single character.)
I've run into a bug where certain styles of Courier Prime turns into ligatures in Google Docs. (Long story short, whether or not ligatures get enabled is a complex interplay between the OS, font, browser, and application, and not every layer always does it right.)
I'm not really sure why font designers even bother creating them in monospace in the first place though, I can't imagine any valid use for them. The only thing I can imagine is if a badly written application forces a ligature character, at least the end result will be readable rather than an empty box or something.