The continent of Guul Draz is a geothermal swampland reeking of heat and decay.

Smoldering Marsh

({T}: Add {B} or {R}.)
Smoldering Marsh enters tapped unless you control two or more basic lands.

Duskmourn: House of Horror Commander

Modern Horizons 3 Commander

({T}: Add {B} or {R}.)
Smoldering Marsh enters the battlefield tapped unless you control two or more basic lands.

Outlaws of Thunder Junction Commander

Even worse, the only toilet paper was locked in a nearby safe.

Fallout

Smoldering Marsh enters the battlefield tapped unless you control two or more basic lands.

Even though these lands have basic land types, they are not basic lands because "basic" doesn't appear on their type line. Notably, controlling two or more of them won't allow others to enter the battlefield untapped.

However, because these cards have basic land types, effects that specify a basic land type without also specifying that the land be basic can affect them. For example, a spell or ability that reads "Destroy target Forest" can target Canopy Vista, while one that reads "Destroy target basic Forest" cannot.

If one of these lands enters the battlefield at the same time as any number of basic lands, those other lands are not counted when determining if this land enters the battlefield tapped or untapped.