Sunbathing Rootwalla
Creature — Lizard
Domain — 
: Until end of turn, this creature gets +1/+1 for each basic land type among lands you control. Activate only once each turn.
A rootwalla's prey includes anything or anyone that wanders into view.
Campbell White
Dominaria United (DMU)
• #181Rulings
Domain abilities count the number of basic land types among lands you control, not how many lands you control or how many of any type.
(wotc • 2022-09-09)
The basic land types are Plains, Island, Swamp, Mountain, and Forest. Land types other than basic land types (such as Desert) don’t contribute to domain abilities.
(wotc • 2022-09-09)
Rulings
Domain abilities count the number of basic land types among lands you control, not how many lands you control or how many of any type.
(wotc • 2022-09-09)
The basic land types are Plains, Island, Swamp, Mountain, and Forest. Land types other than basic land types (such as Desert) don’t contribute to domain abilities.
(wotc • 2022-09-09)