convert2rhel fails with "CRITICAL - Could not find any kernel from repositories to compare against the loaded kernel"

Issue

convert2rhel fails with:

TASK - [Prepare: Checking if the loaded kernel version is the most recent]
CRITICAL - Could not find any kernel from repositories to compare against the loaded kernel.
Please, check if you have any vendor repositories enabled to proceed with the conversion.
If you wish to ignore this message, set the environment variable 'CONVERT2RHEL_UNSUPPORTED_SKIP_KERNEL_CURRENCY_CHECK' to 1.
No changes were made to the system.