A further development of iA Writer Mono (based on IBM Plex Mono) and Duo (2017), made by Oliver Reichenstein and included in iA Writer 5.2. iA Writer Quattro shares more similarities with a proportionally spaced typeface.
Contributed by Citationsy
Contributed by Kenneth Ormandy
Contributed by JJ Ying
Contributed by Daniel McQueen (TDF)