From https://developer.wordpress.org/themes/functionality/internationalization/
Themes that are hosted on WordPress.org the text domain must match the
slug of your theme URL (wordpress.org/themes/). This is needed
so that the translations from translate.wordpress.org work correctly.The text domain name must use dashes and not underscores and be
lowercase. For example, if the theme’s name My Theme is defined in the
style.css or it is contained in a folder called my-theme the text
domain should be my-theme.