First and foremost your dog should be obedience trained and at least know the recall (come command) off leash.
Yes its true that many dogs & cats get along very well. Its usually dogs that are gentle and friendly and dont have a high predatory drive. If they were raised together since babies the odds improve. Even those dogs who do chase small prey outdoors can often learn not to chase or harm cats indoors once they’ve grown accustomed to their household cats as family members. It may actually take longer for your cat to accept the new dog than the