I will say that I had the same or similar issue after upgrading to 26.0.1-ci.4. Upgrading to later versions (26.0.2) didn't fix the issue for me. In my configuration I had the 'Use LDAPS and bypass certificate errors' enabled, as I had not yet installed my internal Enterprise CA root and sub CA certificates to the docker container. Does this apply to your configuration?
I installed them using process documented here: https://docs.inedo.com/docs/installation/linux/installation-troubleshooting-docker-installations#cannot-connect-to-services-that-use-a-self-signed-or-an-internal-certificate-authority and this resolved the login issue for me. I still have an issue where the Active Directory Group used to grant access to my team no longer works, and I have had to grant my team members access individually.