Im 4 years still waits marketplace. Maybe Epic wants for Linux users not buy on Marketplace =)
Im done 3 games on other engine while i waiting.
One is 2d and released on Steam. Named Reskue.
Im dev retro and indie. but still interests UT4 on Linux.
Im previous work with UDK 3.5 (UE3.5) its works perfectly but models have been preloaded for UDK.