Quarantine (https://quarantine.softwarerero.com/) models a worst case scenario for getting herd immunity.

Duobiblo (https://app.duobiblo.com/) allows to practice a language showing chapters of the bible side-by-side with a language you already know. I learn Portuguese currently on Duolingo, which inspired the name. If a browser supports the Web Speech API for the given language it is also possible to let the browser read the text.