Dynamax Adventures (Only available once you've bought the Crown Tundra DLC) have a 1/300 chance to yield a shiny Pokemon.
Using the Masuda Method while you have the Shiny Charm gives you a 1/339 chance of hatching a shiny Pokemon.
And, just recently, a new shiny hunting method was discovered. It allows more encounters of a specific Pokemon, speeding up shiny hunting.
