It can also disable animation in the web browser. Some website can see this setting and disable some stuffs.

There is librelingo but, honestly, it’s far behind Duolingo.

The closest software I found is to use a flashcard tool (like AnkiDroid) and then search for an open deck of your language using AnkiWeb.

Doing so you get a similar experience than DuoLingo without the gamification and pretty UI.

Which tool do you use to re-encode everything to opus ?

I tried with ffmpeg and it works but I had many issues with covers.

I agree it’s seems like a subset of YAML.

IMO it must be a YAML because there is a lot of tool and libraries existing for this language. You can easily build a syntax validators for you schema and it allows developer to extends it easily.

Or an alternative solution could be to use more the YAML frontmatter to put the data.

GNOME, for sure. It works out of the box, and it’s kind of pretty out of the box.

I also tried it on a touch screen PX and it works surprisingly well.