TYPO3 Core

"Form: YAML Configuration" is not available in the drop-down list of the Configuration module.

I think it's a problem of extension loading order, the Form extension being loaded before the Lowlevel extension.
So if($containerBuilder->hasDefinition(ProviderRegistry::class) condition in EXT:form/Configuration/Services.php is not TRUE.
Add ['constraints'=>'suggests'=>'lowlevel'=>'12.4.9'] in EXT:form/ext_emconf.php should solve the problem.

['constraints'=>'suggests'=>'lowlevel'=>'12.4.9'] can also be added for Reactions extension and Webhooks extension, which have the same configuration, even though they load naturally after Lowlevel extension.