What it means is: even after version 1.6 in Linux, Blockly is included as a plugin and not as a standalone program. This means that, just like in version 1.5.5, you start aseba studio, then on the bottom left panel you can click on "start Blockly".
it really is the same version of blockly, just packaged differently. No need for web bridge.

we are working on version 1.7, all this will be simplified, there will only be one app, from which you choose your robot, the programming language, and it starts :) hopefully very soon.

So I finally managed to have everything running.
On top of the above steps I also had to clone and build the repository at
https://github.com/Mobsya/thymio-blockly-standalone

then 1) launching the aseba web bridge and 2) opening to the relevant 'index.html' page from this last package was all I needed to be able to use blockly with thymio.

The full install procedure was not very easy, but I guess it will be once proper linux package (flatpack ?) are avaible.

Anyway thanks imensely to all the team behind Thymio and Aseba !

Thanks for the answer !
I found the statement here :
https://www.thymio.org/fr:blocklyprogramming
"La nouvelle interface Thymio Blockly n'est pour le moment pas disponible sur Linux."

Now, I've tried anyway. As I run fedora 29, I've followed the compilation instruction as suggested from :
https://www.thymio.org/fr:linuxinstall
and followed :
https://github.com/aseba-community/aseba/blob/master/docs/en/development/building.rst

git cloned, compiled.
I have a working asebastudio and also a working thymiovpl executable.
A "web bridge" icon in the menu exists. It visibly starts a asebahttp process… But I find nothing related to blockly… do I need to point my browser to a specific page ?

Thanks again !

where did you see this statement? as far as our team at Mobsya has tested, it works just fine on Linux. did you experience problems?

I see on the web site that the web bridge enabling to program thymio with blockly is not yet available on linux…

How far are we from there ? I ask because if there's a chance of getting it working by easy hacks and/or using the right commands/instructions, I'm willing to try ! In this case where should I look for documentation on those topics ?

Thanks for any hint !