The easiest way might be to decide if you are going to ride with a group and see what they are riding. If you don’t have a group to ride with or check out then you have to decide what kind of riding you will like to do. Road bikes are best for road riding, MTBs are best for dirt riding. Anything else is a compromise that you may or may not like over the long run. I know people that love their flat bar road bikes. I even bought one because of recommendations I have read. But it was best for short commutes and coffee shop rides at least for me.
If you get a drop bar bike you will get used to bifters and riding on the hoods so you are close to the brakes much of the time. If you get a flat bar you will learn to search for the right grips and sooner or later end up with bar ends to increase hand positions as you ride farther.
But the truth is if you discover that cycling is for you this will not be your last bike. It will simply be the bike that teaches you what bike you really want. You will be infected with the N+1 disease and there is no real cure.