TYPO3 Core

It is a non-composer installation. I had to find out why the install tool is not accessible on a TYPO3 site from a different provider. That web seems to have been updated from a prior TYPO3 version to 9.5.28, but I don't know what actually was done.
I saw that the entry for 'install' (and also for 'backend') was missing in the PackageStates.php, so neither backend nor install tool were accessible.
In order to reproduce this, I manually deleted these entries in a local TYPO3 10.4.18 instance and got the same result.

Hmm, but how can a PackageStates.php be created without these entries? If no PackageStates.php exists, then these entries are ALWAYS added. I mean, sure we can add a check for "always installed extensions" when we have a corrupted PackageStates.php but this would add a huge complexity for our code-base, when people manually modify this file. This isn't intended, maybe we need to clarify this in the Documentation?

Just had this bug with a composer-based installation. Info here helped me fix the problem.

I made a copy-paste typo in my AdditionalConfiguration.php with something like that:

$GLOBALS['TYPO3_CONF_VARS']['BE'] = 'be_MYPROJECT_user';
$GLOBALS['TYPO3_CONF_VARS']['FE'] = 'fe_MYPROJECT_user';

instead of

$GLOBALS['TYPO3_CONF_VARS']['BE']['cookieName'] = 'be_MYPROJECT_user';
$GLOBALS['TYPO3_CONF_VARS']['FE']['cookieName'] = 'fe_MYPROJECT_user';

Running composer update broke the loading of extensions and generated a nearly empty typo3conf/PackageStates.php but I didn't see it.

From there on, no way to get back to a working install until I deleted that file PackageStates.php. Only then could it be properly regenerated after my typo.

Possibly this helps someone else.