The following is a collection of information about the use of ttf Fonts that work with App Inventor since the release of nb191 and Companion 2.66 . Here is an example of some of the fonts I loaded.
Label1, Label2, Label3, Label4, a ListView, a CheckBox, ListPicker, a Button, DatePicker, Switch, Textbox with test, TextBox with material design font.
Examples of imported ttf fonts shown in various Controls.
Static ttf fonts work with the new Font control; variable fonts (customizable typefaces) do not.
Static ttf fonts are useful in DeviceDefault and Classic Themes.
Where can you use these fonts?
ttf fonts work in Label, Button, ListView, CheckBox, Switch, TextBox components
Partially works in ListPicker, DatePicker where you can name the control but does not work in the displayed List or dates.
Feature is not available in Screen1.Title, Notifier, Spinner,Canvas
Where to acquire "free" ttf fonts for use in your Projects:
Google the web for more other sources.
Beware; some fonts are NOT free. Use of copyrighted ttf fonts can require a license. An example is many if not all Microsoft ttf fonts; you cannot use them in your Project, especially if you will sell the app to others.
Be a good neighbor.
Material Design Icons ... mic play_arrow skip_next Type the name of the icon to render it's image.
Link to Google Material Design ttf
This is a list of icons and Android 'names' Google Icons Intro
How to import ttf fonts from the Web
Go to https://fonts.google.com/ then follow the following flow schematic.
Custom font typeface support made possible in App Inventor by @preetvadaliya .
Have fun and find interesting uses for the custom fonts available.