Hello,
like i understand the latest version it tooks from the List always the first that is possible in py2saml
And that is always redirect if IDP supports multiple.
But with redirect and http/2 the header is huge and IDP crashes with Header Size to high.
Its recommended to use POST for these cases.
Actuall there is no way to tell the system to use POST for the binding to the IDP request, if both sides SP and IDP support redirect and POST.