It’s not very common to develop libre roms for real consoles, but there is an quite active “fantasy console” scene. A good open-source example is: https://tic80.com/

Some quick links:

• https://itch.io/c/1044509/list-of-nes-homebrews
• https://itch.io/c/1024610/nes-homebrew-games
• https://nesdoug.com/2017/10/31/a-list-of-nes-homebrew-games/
• https://github.com/retrobrews/nes-games
• https://www.romhacking.net/?page=homebrew&category=&platform=1&source=&perpage=20&title=&search=Go

There are some for “fantasy consoles”, but other than that I don’t think there is much point to it as you can more easily make the homebrew game native.