How do you get into the 8th gym?

In Pokémon Sword and Shield, the eighth gym is Ballonlea Gym, led by Raihan. To get into Ballonlea Gym, you will first need to earn seven gym badges. Once you have done this, head to Circhester City, where you will find a train station. Take the train to Ballonlea, and you will arrive at the Balloonlea Gym.