Alert key has yet to be disclosed. The alert system itself has been retired for quite a while now. More information about this can be found here:
https://bitcoin.org/en/alert/2016-11-01-alert-retirement
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016-September/013104.html

Recently it was suggested to me that it would be helpful to wait for v0.13 end-of-life before revealing the alert keys.

I am seeking information regarding anyone that has requested final alert messages for any particular projects that may have copied the bitcoin alert pubkey.

Thank you.