Whenever I try to search for The Legend of Zelda, Super Mario Bros. 3, Super Mario Bros. 2, and Super Mario Bros. I get an error message at the bottom that says "Sorry, we couldn't load the data. Retry. But if I click the retry button it'll just reappear like 30 seconds later and I can't get rid of it unless I completely shut down the software and relaunch it.

Sidenote; Donkey Kong Country 1 and 2 don't show up in the game library, even after restarting the app. I don't know if this is a common issue that's already been fixed via a plugin or not but if that's the case please leave a link to the github in the comments.

That sounds like a problem with the search, but Nintendo isn't going to port any of their games to PC, let alone old ones.

I can reproduce the issue...

I suppose the Database contains only PC games and modern consoles.

Anyway the error given by Galaxy is just a client issue...

To stop the client to constantly showing that error message just do another search for a pc game (example "spellforce").

You can see that during the search there's a rotating icon, if it disappear after the list is displayed then there are no errors... if instead it keeps rotating, then you will keep seeing the "couldn't load data" popup.

Galaxy's source for the search is www.igdb.com. Galaxy sents a request to igdb with the search parameters you typed in and recieves an JSON object with possible search results.

now, if you type in something like "super mario" or "legend of zelda" you get an error message. probably because the result you get from igdb has some broken entries or content which Galaxy can't process.

You can at least get to and mark Legend of Zelda as owned, if you just type "zelda" in the search, but for the Super Mario Bros games, i was not able to find a way.

It's still possible to add these games with plugins to your library, but this is more laborious.