After you get the eighth and final Gym Badge, you take the train to White Hill Station on Route 10.
Explore the Route
Go west from the station and check on the sparkle to get 2 X Attacks.
Go east. The pokémon that you may see in this area are Cubchoo, Glalie, Mr. Mime (Galarian Form), Snover, and Vanilluxe. The pokémon that can be found in rustling patches of grass are Darumaka (Galarian Form), Klang, Rhydon, Snom, and Vanillish.
East of the grass, there is a Max Revive.
North of the grass, you will battle Doctor Graham, who has a level 45 Gardevoir. You get 5400 Pokédollars for winning.
Go north and you can battle Hiker Douglas, who has a level 45 Steelix and a level 45 Mudsdale. You get 4500 Pokédollars for winning.
To the north, the path splits. If you want to have a wild pokémon encounter with Abomasnow, go northwest to find one. Otherwise, if you go northeast, you can battle Office Worker Ronald, who has a level 45 Weavile and a level 45 Claydol. You get 3600 Pokédollars for winning.
Northeast of there, check on the sparkle in front of the rock to get a Comet Shard.
West of that, you can battle Cabbie Geoffrey, who has a level 45 Corviknight and a level 46 Flygon. You get 5520 Pokédollars for winning.
North of that, you can battle Postman Harper, who has a level 46 Pelipper and a level 46 Noctowl. You get 4416 Pokédollars for winning.
Go west and look for a southern path just west of a group of rocks. Go south along that path to find a Power Herb.
Keep going west and you eventually find Tristan's Pokémon Camp. This is added as a Flying Taxi destination.
West of the camp, check on the sparkle to find a bottle of PP Up.
Go north from the camp and you will battle Hiker Donald, who has a level 46 Gigalith and a level 46 Rhydon. You get 4600 Pokédollars for winning.
Go north and you will battle Gentleman Glenn, who has a level 46 Darmanitan (Galarian Form), a level 46 Falinks, and a level 46 Grapploct. You get 9200 Pokédollars for winning.
Go north and you will have a double battle with Interviewers Gillian and Cam, who have a level 46 Klinklang, a level 46 Heliolisk, a level 47 Togedemaru, and a level 47 Noivern. You get 9400 Pokédollars for winning.
Go north and you will arrive in Wyndon.