What is a monospace font in iOS?
Solution 1:
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.
Solution 2:
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.