I solved this issue for my girlfriend quite easy to be able to login to the dashboard again.
when you get the website with the “No update required” message, don’t click on continue but instead goto the adres bar.
it should say something like:
https://DOMAINNAME/wordpress/wp-admin/upgrade.php?_wp_http_referer=%2Fwp-admin%2F
Simply remove the text in the url behind wp-admin and press enter.
So remove: /upgrade.php?_wp_http_referer=%2Fwp-admin%2F
(This removes redirecting to the upgrade)
You should get the dashboard login.
It worked for our problem.