ramrajone
Sorted the php back to 7.2 and now I see the user note about being offline if I go to the main site page.
But, if I try to login as an agent expecting to see the upgrade option, I receive the "valid CSRF Token required" message.
As a test, I removed my ost-config.php file and (the setup folder is there from the 1.11 update) I get the install screen. So something is twisted in my config.php file, but that is unchanged from before the DST change.
Also - the CSRF message is in the error.log, but there is nothing that seems unusual in the php logs.