Currently it is not possible to link multiple URLs or website to specific IdPs if using SSL. If you are hosting multiple websites and want to use different Identity providers for each of them that's not possible.
SNI might be required for this. See: https://domino-ideas.hcltechsw.com/ideas/DOMINO-I-15
/application1.nsf => SAML IDP 1
/application2.nsf => SAML IDP 2
Or like this as an alternative:
/application1.nsf => xyz.company.com => SAML IDP 1
/application1.nsf => abc.company.com => SAML IDP 2