Custom fonts can be used in the Iterate survey view by adding the font files to your assets folder, and passing their paths (relative to /assets) to the Iterate.init method, like this:
Iterate.init(this, API_KEY, null, "Merriweather-Regular.ttf", "WorkSans-VariableFont_wght.ttf")
The font specified in the buttonFontName parameter will be used in all survey interface buttons (question responses, previous / next buttons, etc). The font specified in surveyTextFontName will be used for all other survey text (question prompts, explanatory copy, etc).
True Type fonts and Open Type Fonts are supported.