Sinnoh Ground Types: How to Complete the Throwback Challenge

Sinnoh Ground Types are on the docket for players looking to complete the Sinnoh region throwback challenges in Pokémon GO's current throwback event. These Pokémon will be available only for a limited time, and completing the challenges earns in-game rewards for players, doubling up the incentives to get catching. Here's how to complete the challenge.
Trainers, Pokémon originally discovered in the Sinnoh region are now appearing more frequently in the wild, hatching from 7 km Eggs, and being featured as exclusive Field Research task reward encounters! https://t.co/dcnLLx78wU pic.twitter.com/qRNBE3c8MT
— Pokémon GO (@PokemonGoApp) May 22, 2020
Sinnoh Ground Types: How to Complete the Throwback Challenge
From Friday, May 22 to Friday, May 29, players will be able to catch Pokémon native to the Sinnoh region, first introduced in Pokémon Diamond, Pearl and Platinum. Catching just one Ground-Type Pokémon will complete a challenge in Step 4 of the Throwback Challenges, earning a Skorupi encounter.
Two Ground-Type Pokémon, Hippopotas and Gible, appear in the wild. Both are rare, but will typically be found in parks, woods, farms, and hiking trails.
Players can also acquire Ground-Type Pokémon and complete the challenge through Battle League reward encounters with Larvitar or Stunfisk, by finding Hippowdons in Tier 4 raids, or by using Magnetic Lures to draw out an Onix or Alolan Diglett.
The most surefire way to find a Ground-Type is to complete the Hoenn challenge "Earn a Heart with Your Buddy," which gives a free Marshstomp as a reward.