LaunchDarkly supports only IdP-initiated SSO:
Identity Provider Initiated (IdP-initiated) SSO. With this option, your end users must log into your Identity Provider's SSO page (e.g., Okta, OneLogin, or Microsoft Azure AD) and then click an icon to log into and open LaunchDarkly the web application.
Service Provider Initiated (SP-initiated) SSO. LaunchDarkly does not support this option: This option gives your end users the ability to sign into the apps Login page and then sends an authorization request to the Identify Provider (e.g., Okta, OneLogin, or Microsoft Azure AD). Once the IdP authenticates the user's identify, the user is logged into app.