As long as you keep it fair, as in not many users, not too many streams etc, https://fairmeeting.net/ offers videocalling for free. I think it is using Jitsi.

They also offer paid versions that you can use should you require more than a few users.

It is not as game-ified, but you can have a look at anki. There are plenty of premade decks about various topics to learn with.

There are a few other providers that do lifetime subscriptions. Filen.io and pCloud come to mind.

Well, now it can

It is from an audiobook made by a German public broadcast service. It is called GRËUL. Set in the Middle Ages, and revolves arouns a valley of not-yet christianized mountain people.

It is only available in German though.