What is a monospace font in iOS?
iOS mono-spaced fonts
Courier Courier-Bold Courier-BoldOblique Courier-Oblique CourierNewPS-BoldItalicMT CourierNewPS-BoldMT CourierNewPS-ItalicMT CourierNewPSMT Menlo-Bold Menlo-BoldItalic Menlo-Italic Menlo-Regular
iosfonts.com maintain a list of all iOS fonts.
This webpage detects your installed system fonts and returns a fairly comprehensive list.
Looking at an old listing of fonts shipped with iOS I see several one monospace fonts.
(eg. Andale Mono, Monaco, Courier New)
For 2018 it's only Menlo and Courier.