The intended way is to travel the map from the Normandy HUB, select a system to explore, and pick a planet within it to visit.
Not all planets can be landed on, however. The ones that DO count often have a cutscene of an incoming transmission the first time you visit, usually asking for help, but not always.
You don't have to do the missions, just landing on the planet is enough!
However, because of all the loading screens from jumping between star systems and choosing a planet which may or may not be counted for the Trophy I opted to do it the cheap way which uses only ONE planet.
Go to Argos Rho on the map and enter the Hydra system. Metgos, the 2nd planet up from the sun, is a planet you can travel on.
Select it, pick your crew and once you land in the vehicle press
and return to the Normandy. When you're back on the Normandy rinse and repeat the process.
As of this writing (Apr 23, 2023) this method works and takes 5 to 10 minutes.