Deep linking for IdP-initiated vs SP initiated SAML

I am looking at the documentation for IdP and SP initiated SAML and seem to come across conflicting information if the IdP-initiated SAML supports deep linking. From what I understand, myDomain is required for deep linking in both cases (though generally optional for IdP-initiated SAML) and the IdP must support the RelayState parameter, but then I see other posts saying that only SP-initiated SAML can support deep linking. So which one is correct?

#SAML Single Sign On #Deep Links #IdP Vs SP #Identity and Access Management