26 cards where the card types include “desert” and the color identity ≤ GRW and (the card is available on Paper)

Abraded Bluffs (Outlaws of Thunder Junction #251)
Arid Archway (Outlaws of Thunder Junction #252)
Bristling Backwoods (Outlaws of Thunder Junction #253)
Bucolic Ranch (Outlaws of Thunder Junction #265)
Cactus Preserve (Outlaws of Thunder Junction Commander #40)
Conduit Pylons (Outlaws of Thunder Junction #254)
Cradle of the Accursed (Amonkhet #241)
Creosote Heath (Outlaws of Thunder Junction #255)
Desert (Forgotten Realms Commander #233)
Desert of the Fervent (Outlaws of Thunder Junction Commander #284)
Desert of the Indomitable (Outlaws of Thunder Junction Commander #285)
Desert of the True (Outlaws of Thunder Junction Commander #286)
Dunes of the Dead (Outlaws of Thunder Junction Commander #291)
Endless Sands (Commander 2020 #272)
Grasping Dunes (Amonkhet #244)
Hashep Oasis (Outlaws of Thunder Junction Commander #299)
Hostile Desert (Murders at Karlov Manor Commander #266)
Lazotep Quarry (Modern Horizons 3 Commander #79)
Mirage Mesa (Outlaws of Thunder Junction #262)
Painted Bluffs (Outlaws of Thunder Junction Commander #309)
Ramunap Ruins (Outlaws of Thunder Junction Commander #311)
Sandstorm Verge (Outlaws of Thunder Junction #263)
Scavenger Grounds (Outlaws of Thunder Junction Commander #316)
Shefet Dunes (Outlaws of Thunder Junction Commander #318)
Sunscorched Desert (Amonkhet #249)
Survivors' Encampment (Hour of Devastation #184)

The message was clear to Sorin—time to search for something else.