What is the ruling on praying Fajr alone in the mosque immediately after waking up, performing the iqamah, and missing the congregational prayer?

As long as the reason for missing congregational prayer is sleep, there is no sin upon you; for the pen is lifted from the sleeper until he awakens. If you are able to attain the virtue of congregational prayer at another mosque from which you can hear the call without a loudspeaker, then you should go there. Your prayer performed alone is valid, Allah willing.