Actually, the Lions did win a "real" playoff game back in 1957.
The Lions and 49'ers tied for what was then known as the Western Conference of the NFL.
A playoff game was held in Kezar Stadium in San Francisco on December, 22, 1957.
The Lions won 31-27 and thereby made the NFL Championship Game.
So yes, the Lions have won a road playoff game - you just have to go back 66 years!
https://en.wikipedia.org/wiki/1957_NFL_playoffs
https://www.profootballhof.com/football-history/1957-playoff-game/