Whaaaat no that’s not disgusting at all! This forum is filled with poop stories - people talk about it all the time (myself included!) - even posting pics of poop to check on it. Feel free to post Rambos if you’d like and we can take a looksie. Poop and urates can honestly tell a lot about a dragons health
So the white you are seeing is Rambos urate - aka their way of peeing - it’s often white and can be yellowish in colour. And, his poop being the colour green / brown is normal (or at least those are the normal colours for my girl as well).
Their poop is often formed with the addition of a urate to accompany it. Sometimes you’ll see a larger urate to poop ratio - more often you’ll see a larger poop to urate ratio. This kind of all depends on how much food vs water your dragon is taking in on any given day.
So I would say if he is indeed 5 months old, and eating often like a 5 month old can do, his poop is pretty well formed (not super runny or diarrhea), and the urate is looks/feels normal (not solid as a brick / able to break up) then he sounds good to go. Do these things line up with what you’re seeing regarding Rambo?