By default draw.io uses the language of the browser installation. Is it possible to override that setting?
There are menus to change the default language for your browser in two places. At the bottom right of the initial splash screen there is a little "world" icon:
You can select a new language and refresh the page for that to take effect.
The world icon also appears at the right of the menu bar while using the application:
If you want to test a language without persisting the language setting, you can use the lang parameter in the URL following by the two letter country code, e.g.www.draw.io?lang=es.