Depends.
If you can sideload games on the console, you can also upload and distribute it on itch. There is this Playdate console https://itch.io/games/tag-playdate , so the trivial answer to your question is: Yes.
You will also find roms for other consoles, even c64. PSX looks popular.
Just putting a page up with the link to another store is kinda pointless. And maybe even against the tos.
But you will find things that are available on itch, but will have links to steam, the apple store, the google play store and so on. I do not remember seeing a link to playstation or xbox though.