Dogs tend to jump up during greetings because they want the person’s attention (e.g. eye contact, touch, voice). To some dogs, even “negative attention” like pushing the dog away, scolding, etc. can be reinforcing, making the jumping up even worse.
The best solution I’ve found is to give the dog attention ONLY when the dog’s four paws are on the ground. Remove your attention (eye contact, voice, and touch) when the dog is jumping up on you — turn your head away for a clearer message. Wait for the dog’s paws to return to the ground. If the dog seems to be “hanging on” you can turn your whole body so the dog’s paws slide to the floor. The instant the dog’s paws are on the ground, you can offer a small amount of attention — perhaps look at the dog briefly and smile, then look away and return you gaze in small doses — too much at once is too exciting. You could instead choose to speak to the dog (e.g. praise) in a calm voice, or perhaps let the dog sniff, lick your hand, or a calm and brief pet or two. You want the attention you give to be small doses.
What will likely happen as your dog is still learning, is that the dog will jump up again after a bit of attention. Just remove your attention again and wait for the dog to put paws on the ground. You may have to step behind a barrier to let your dog calm down a bit. Avoid giving any attention to the dog if you can unless the dog is calmer and has four feet on the ground. Eventually your dog will figure out that his/her behaviour can make you give some attention (what the dog wants) AND that his/her behaviour can make you remove your attention (the opposite of what the dog wants).
Start with waiting for four paws on the ground, but over time you can progress to expect a bit more from your dog (e.g. a SIT for the greeting). You’ll want to practice SIT in other contexts so that your dog is better able to perform in an exciting environment.
Contact me if you would like further instruction on this or other dog training & behaviour.