If Moodle Themes do not specify they use FontAwesome in their config file or implement a custom icons system Moodle core provides fallback icons.
See for example this screenshot from boost where
$THEME->iconsystem = \core\output\icon_system::FONTAWESOME;
is commented out in the config.php
Currently some of these fallback icons are missing and it takes time to maintain them, and if themes do not use FontAwesome for their icons, will they want to have the fallback versions which look outdated?Are there any themes that need the fallback icons or would it be okay to remove them in core? It would be great to get some feedback on that from the community here on on https://tracker.moodle.org/browse/MDL-61544