Looks good to me, I tested a few activities and didn't noticed any bug. There are still some png (but not big files so we won't gain much by converting them to webp):
src/activities/hangman/resource/fog.png
src/activities/memory-sound/resource/Tux_mute.png
src/activities/memory-sound/resource/Tux_play.png
src/core/resource/aboutkde.png
src/core/resource/arrow.png
src/core/resource/gcompris-icon.png
src/core/resource/gcompris.png
src/core/resource/star.png

sure, you can work on it. It's the "target" activity (you can search it in the search bar): https://gcompris.net/screenshots_qt/middle/target.png

@hadron if you think you will have time, feel free to take a look at it, you'll probably find a cleaner quicker solution than me :). If you don't have time, please tell so another person can take a look at it

other debug dll removed in https://invent.kde.org/education/gcompris/-/commit/b14adfa8261c98a9527adc1c715987c975a91849

Last task will be to remove the QtQuickControls debug dll (happens also when migrating to QtQuick Controls 2)

imageformats have been cleaned in https://invent.kde.org/education/gcompris/-/commit/d5ec598d487a352bf1a6c00a3b2f5f252091f819. It seems to only affect Windows

WIP in https://invent.kde.org/education/gcompris/-/merge_requests/106

For lang, we go from 59.7Mo to 40.2Mo with a conversion of all png with no loss (magick $f -quality 100 -define webp:lossless=true $f.webp), so for me, it's a go :).

The initial positions are hardcoded in https://invent.kde.org/education/gcompris/-/blob/master/src/activities/traffic/traffic.js

In T15303#271409, @echarruau wrote:

We should also add some sentences to the second level.

Maybe a third dataset, above 10 words would make sense?

I agree with point 1.
For 2, I would keep the parenthesis.
For 3, against Tux.
For 4, with a friend

https://invent.kde.org/education/gcompris/-/merge_requests/95

Calendar has been added in Qt6.3: https://doc-snapshots.qt.io/qt6-6.3/whatsnew63.html#qt-quick-controls-module. As it is not a LTS, we'll need to find on how to handle it... Maybe copy the code of the module when we use Qt6.2.
We need to check the effort of having it in Qt5.15 (5.12?), it could solve some of our current issues too.

Other issue to dig in is to know if it is possible to know if there is a mouse or not when starting GCompris. If there is not a mouse, then we should disable the activity.

In T15130#269879, @timotheegiet wrote:

News added and info for android updated on the git repo.

Yes, if we can keep a track of the versions, it is even better :)

@timotheegiet here is a proposal for the website: https://hebdo.framapad.org/p/release2_1. Feel free to update it and commit as soon as you want (so we can have translations for the release :)).
I removed the number of totally translated languages, because technically, we only have 13 fully translated as most didn't update the changelog. But the changelog is only visible once so I think we can consider them as 100% translated.

There is no need to push too much the independency. In all cases, the website uses the content of the ActivityInfo.qml so we need to download the GCompris source. We could split the translated strings of ActivityInfo to a separate .po file but there won't be too much gain out of it..

Fixed in https://invent.kde.org/education/gcompris/-/commit/f0ce2b9b996f02f16ba9d694fbdd6e3097cf9263