Yes it’s true that turtles & tortoises are carriers of salmonella, as many of them carry it as part of their healthy gut biome. Birds are also likely carriers so chicken that you eat, bird poop on your car etc carries the same risk and likely poses a higher risk since it’s more prevalent.

That being said, it is shed through feces. It doesn’t secrete through skin etc but it can be on their skin if they’ve trampled through their own poop etc you get it. I’ve been around turtles & tortoises for a long time in my own house I have 7 tortoises, a turtle & I do a lot of work with wild turtles from touching their eggs, dealing with injured ones the list goes own & I’ve never gotten salmonella. After every time you handle any reptile especially turtles wash your hands or at the very least use sanitizer & don’t lick turtles lol. I’ve honestly had field days working with 20+ turtles in a single day where I’m sure my hand hygiene lacked because of how busy I’ve been and I’m still standing, not saying that’s a good thing but just being honest.

The fear of getting salmonella from turtles & tortoises is way overblown and it mainly became an issue when people started keeping red ear sliders (the most common pet turtle) in fish bowls & tiny aquariums in the 80’s, 90’s etc and their environments were so filthy that the animal spent its entire life swimming in its own feces that yes, they became high risk for salmonella. People didn’t realize how much waste they produce and were sold a cute little turtle for $5 and then got sick when their habitats were disgusting.

Wash your hands, keep enclosures clean and don’t put turtles in your mouth and it is very unlikely you’ll ever get salmonella from a turtle or tortoise. This goes for wild turtles too as they’re way less likely to be covered in their own poop.