I upgraded from Moodle 3.10 to 4.0.1+
I got errors in the website-adminstration:
Undefined property: stdClass::$enableaccessibilitytools in D:\Inetpub\....\blocks\accessreview\block_accessreview.php on line 176
The plugin "accessibilitytools" was not enabled automatically during the upgrade.
I could solve the problem by activating accessibilitytools at website-administration --> advanced features --> activated the checkbox for accessibilitytools
Afterwards the problem was solved but it took quite a while to figure out the cause.
OS: Windows 2016 + IIS + PHP 7,4,29 (64 Bit)
The extension should be activated automatically during upgrade or moodle should run with deactivated accessibilitytools.