The wilds of Athas are a treacherous place, and the skills of a ranger are most often learned as a guide, hunter, or scout for a military operation. Rangers are found in every race, most prominently among halflings. To the ranger, the seared lands are not an enemy but a well respected adversary. Rangers generally are on good terms with druids, and it is from a druid mentor that a ranger likely has experienced contact with a Spirit of the Land that can bestow upon her certain powers.
Use the defaults from the Player's Handbook or Xanathar's unless changes are mentioned below. From any other book please check with the DM.
Remove celestials, dragons, and fey.
Replace terrain with Sandy Wastes, Stony Barrens, Rocky Badlands, Salt Flats, Scrub Plains, and Silt. Forest may be added at DM discretion but is virtually unknown to any but halflings.
Difficult terrain does not slow the ranger's travel but still affects their companions. The ranger gains advantage on navigation checks, not automatic success.
Spell changes. The spell goodberry does not exist.
Horizon Walker (Xanathar). Does not exist.