I am curious about how to broadcast an alert. I know that this is possible because the system to send alerts has been shut down and this probably won't work, but I am curious about how I can broadcast an "alert" using bitcoin-cli.
bitcoin-cli has never had the capability to send alerts. It is not possible for a user to push out an alert from any Bitcoin Core node.
Alerts were sent by using a specially modified version of Bitcoin Core which had the particular alert to be sent hard coded into it. Developers have to modify Bitcoin Core and include the alert code in a local build every time they wanted to send an alert.