N.B. : To be clear, in the video, the left Joy-Con is working and the right Joy-Con is defective, the order I followed depends on which Joy-Con is broken.
I found a very simple workaround to use my right Joy-Con as a single controller without having to use the SL & SR buttons.
From the home menu, you just have to :
Detach the other Joy-Con (the one with the SL/SR buttons working) and change it's mode to sideways via the "Change Grip/Order" menu
Reattach this Joy-Con back on the console
Detach the defective one
Now you can see that the defective controller is automatically put in sideways mode!
Start any multiplayer game and enjoy!
We are able to play Smash without any problem as all the buttons are remappable!
For your information, at the time of writing, my console's version is 8.0.0.
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