LG 24GM79G-B 144Hz TFT here, bought November 2017 and no explicit DAS option or reference in any of the menus.
I assume its enabled automatically when in one of the gaming modes.
From what I can infer from the dubious marketing fluff on the LG website, DAS is just what LG call their 'straight through' mode which minimises processing to reduce latency as far as possible.