I was thinking about general SW gaming today, and realised that whole Republic Commando thing came and went. I think they got one blink and you’ll miss it appearance in TCW. Were they ever a thing anywhere else?

Republic/Clone Commandos are a playable reinforcement unit in EA/DICE’s Star Wars: Battlefront 2 (2017), added in September 2019. As you say, they also show up twice in TCW, first being a cameo from Delta Squad (from the game originally; now their only canon appearance) and the second time being Gregor in everyone’s favourite arc.