I want to be able to have kids to Scratch programming without an Internet connection on an open source desktop distro, in spite of Adobe AIR no longer being actively supported on Linux.

This turns out to be not too challenging. First, get the AIR installer:

$ wget http://airdownload.adobe.com/air/lin/download/latest/AdobeAIRInstaller.bin

Make it executable.

$ sudo chmod +x AdobeAIRInstaller.bin

The AIR installer will complain that it can’t find the GNOME Keychain libraries where it expects to, so let’s set up symlinks for those (this is for a 64-bit system):

$ sudo ln -s /usr/lib/x86_64-linux-gnu/libgnome-keyring.so.0 /usr/lib/libgnome-keyring.so.0
$ sudo ln -s /usr/lib/x86_64-linux-gnu/libgnome-keyring.so.0.2.0 /usr/lib/libgnome-keyring.so.0.2.0

Now, we can run the AIR installer.

$ sudo ./AdobeAIRInstaller.bin

Next, browse to http://scratch.mit.edu/scratch2download and grab the Linux version of Scratch.air. If your browser doesn’t offer to open it with the Adobe Air Installer application when it’s been downloaded, find the file, right-click on it, choose “Open with…”, browse to /usr/bin and select the Air Installer.

You should have a working version of the Scratch 2 Offline editor when the install has completed.