The "honk" is still there, but it works differently as it's now part of the FSS which is built in to every ship. To use it you have to bind it to a firegroup and be in "Scan" mode (blue) as opposed to "Combat" mode (orange).
If you're in a system which has been fully discovered (either by yourself, or someone else, or is a pre-discovered system such as many in the Bubble), then after the "honk" the NavPanel and the System Map are fully populated. You can then use the FSS interface to resolve any Signal Sources if you wish or you can fly around the system as in the past and target them to scan them..
If you're in an undiscovered system then after the "honk" only stars are discovered. You then need to either use the FSS to scan the system, or drop in to the NavBeacon (if there is one) and scan that in order to populate the NavPanel and System Map. For full details on how to use the FSS it's probably best to watch a YouTube tutorial; it's not so easy to describe in words.
Flying near planets automatically scans them as well (no need to target) - this might be why you've had some "Discovered" popups if there were planets within scan range when you dropped out of hyperspace.
There are haters and lovers of the change; make up your own mind.
EDIT: PS, there's a new optional "DSS" module now which allows you to Surface Map planets by firing probes at it. This yields a new "First Mapped By" tag if you're the first to do so as well as more credits. It also reveals the locations of any permanent surface POIs, such as volcanic activity, biological sites, or human/alien settlements.
The functionality of the original "Surface Scanner" is now part of the built-in FSS; the DSS is completely new functionality.