Summary

At the moment, when we set SAML as the primary authenticator, Jira will redirect the users to the IDP login page but, it only happens when they access the page below:

<JIRA Base URL>/login.jsp

When we are in JIRA Dashboard page, CreateIssue page or any other page that is not login.jsp, the redirection would not happen and due to the SAML enabled, the Login gadget is missing to not allow users to log in from this page.

Suggested Solution:

To have JIRA redirect users that are accessing JIRA Dashboard when they are not logging in yet will be great.

Notes:

I can see that this could be a challenge as JIRA Dashboard Page is not just used for login, as we still access the same page after logging in with the gadgets.

<JIRA BAse URL>/secure/Dashboard.jspa

Workaround

If you are not using any features that require public access (such as Jira Service Management's login-free customer portals), you can enable the public.access.disabled dark feature to make Jira redirect unauthenticated users to the login page, as described in How to redirect users to SSO authentication in Jira.

Alternatively, if that isn't possible and you have a limited use-case which involves sharing a one-click link for users to browse the dashboard, create issues or browse any other page in Jira, you can achieve a similar result by ensuring the link goes to:
https://<BASE_URL>/login.jsp?os_destination=%2Fsecure%2FDashboard.jspa
Note that the URL above redirects to the dashboard.