Except when logging in to Google and Jenkins for the first time, Jenkins login incorrectly redirects to JENKINS_ROOT_URL/securityRealm/# (as per attached screenshot).

Scenarios:

A. Signed out from Google (with email pre-populated from previous login); logged out from Jenkins.

1. click "log in" on Jenkins
2. redirected to Google login page; user already known
3. Enter password and request 2FA code to my phone; enter code
4. Jenkins redirects to JENKINS_ROOT_URL/securityRealm/#

B. Removed Google login details; logged out from Jenkins

1. click "log in" on Jenkins
2. redirected to Google login page; enter email address and follow login steps
3. Enter password and request 2FA; enter code
4. Jenkins correctly redirects to JENKINS_ROOT_URL/# 

C. Logged in via Google; logged out from Jenkins

1. click "log in" on Jenkins
2. Jenkins redirects to JENKINS_ROOT_URL/securityRealm/#

My authorised redirect URL in Google oauth client settings is: JENKINS_ROOT_URL/securityRealm/finishLogin