Handheld Electronic Game Platform
This one may look like a stretch, but there are many hardware-exclusive games out there, and it would be the same as the Arcade platform, which isn't, by itself, a concise hardware platform, but a concept.
The only handheld electronic game option on IGDB now is the Game & Watch, but there are many games, even in renowned franchises, for things like the Tiger Electronics and other smaller brands.
The one I got to know recently was the Nelsonic Game Watch series (don't confuse with Game & Watch), which had some games licensed by Nintendo itself, like The Legend of Zelda Game Watch and Super Mario Bros. Game Watch.
Wikipedia on this platform: https://en.m.wikipedia.org/wiki/Handheld_electronic_game
We decided to add Handheld Electronic LCD to cover games like these. This would be the best name to use for now. We are aware that not every game uses an LCD screen, but it's better than to just call it "Screen". Thanks!