I tested some widely available open-source/libre fonts to see which of them best support Cypriot Greek consonant modifiers. Currently, Mozilla’s font Fira Sans has the best support.

PDF Sample file

DejaVu Sans

Good: Breve, Caron

Bad: Subscript-iota

Fira Sans

Good: Breve, Caron, Subscript-iota in oblique

Bad: Subscript-iota in …