This answer addresses Regulation G BSS using Smogon's Viability Rankings.
Ho-oh, Lugia, and Rayquaza are the three Restricted Pokemon higher than B tier that resist Ground.
Dragonite, Landorus-Therian, Ogerpon-Wellspring, Rillaboom, and Gliscor are all above B tier.
Ho-Oh @ Heavy-Duty Boots
Level: 50
Ability: Regenerator
EVs: 252 HP / 252 Def / 4 Spe
Tera Type: Fairy
Impish Nature
- Sacred Fire
- Recover
- Whirlwind
- Brave Bird
Ogerpon-Wellspring (F) @ Wellspring Mask
Level: 50
Ability: Water Absorb
EVs: 252 HP / 4 Atk / 4 Def / 188 SpD / 60 Spe
Tera Type: Water
Careful Nature
- Ivy Cudgel
- Horn Leech
- Encore
- Leech Seed
Rillaboom @ Assault Vest
Level: 50
Ability: Grassy Surge
EVs: 252 HP / 252 Atk / 4 Def
Tera Type: Fire
Adamant Nature
- Grassy Glide
- Knock Off
- U-turn
- High Horsepower
Gliscor @ Toxic Orb
Level: 50
Ability: Poison Heal
EVs: 212 HP / 228 Def / 68 Spe
Tera Type: Steel
Impish Nature
- Earthquake
- Substitute
- Toxic
- Protect
The following Pokemon have many recommended sets. You should pick one based on what your team needs.
Dragonite
Landorus-Therian