What are all the homebrew games on this site (I cannot find any except for the Pringles games)?

You can't search that through the site, but you can use the API.

This API link will return a shortened JSON of all games under "Homebrew" game type: https://www.speedrun.com/api/v1/games?_bulk=1&gametype=z71pomxr

If anyone wants to search games under a different game type, this API link will return all the game types and their id: https://www.speedrun.com/api/v1/gametypes

Just replace the gametype parameter in the link above to the id of the relevant game type.