The latest build of the PTR allows all players to buy Sombra's Demon Hunter skin for 1000 credits. Up till now the skin has been a Blizzcon 2019 virtual ticket exclusive. - )
Demon Hunter Sombra will reportedly be available in 2019 without a BlizzCon ticket - Dot Esports
I Talk on Twitter: "I know this is Overwatch related, but you can actually unlock the Demon Hunter Sombra skin if you complete the Week 3 challenge...this skin was exclusive to Blizzcon
Demon hunter Sombra skin concept, Ben Zhang on ArtStation at https://www.artstation.com/artwork/w88LxV | Concept art characters, Demon hunter, Character art