No way to avoid authentication via previously-used authentication service
In a previous life, I already used https://jupytercloud.lal.in2p3.fr/ with Firefox with my CNRS account (Janus, firstname.lastname@example.org). Now that I click on "Se connecter", I don't have the opportunity to choose my "Établissement" (now I would like to connect with Université Paris-Saclay), I am always redirected to Janus (CNRS authentication).
Of course I looked for cookies, but I don't have any for this domain.
I have seen in the documentation that in some cases one keeps getting redirected to the home page, but the issue I have is slightly different.
I have also seen that it is possible to use private navigation (then I can indeed choose Université Paris-Saclay), but that is not the point, using private navigation should not be required.
It should be possible to reinitialize the choice of the authentication domain ("établissement"), at least by removing cookies.