Well what makes a good therapy dog in the first place is it’s temperament.
Leos in general I think do make good therapy dogs. (Ignoring their size. You can’t necessarily have a Leo jump up in a hospital bed, like a Border Collie might, with someone if they’re not use to their weight and size like an owner would be.)
They are very kind and docile, which makes for a good therapy dog, even though not all are so intuned to their owner/other peoples emotions like other breeds.
But with the temperament of a therapy dog you need a very relaxed, gentle, afriendly dog. I wouldn’t suggest your Leo be a therapy dog if it were hyperactive all the time and didn’t know when to calm down. Most people, when they see a therapy dog, just like the company a dog can bring and their easy affection toward other people.
Now, I know not many Leos are as hyper as other dogs but this is just in the off chance yours might be.
If you do want your dog to be a therapy dog just make sure he/she is ready for it. I wouldn’t have mine be one because she is the type to jump into peoples laps and she isn’t the type to sit for an extended time with someone before she goes off and looks for a cool spot of floor to lay down on, and she is far from gentle.
But if yours has always been one to cuddle in bed with you, or on the couch, and prefers laying with people then I’d say your dog has a good chance at becoming one.