In the release, the BepInEx folder is called "BepinEx" instead. This breaks all mods on non-Windows machines, and some specifically configured Windows ones too.
There is an experimental planet pack currently available. It's BepInEx based, just extract it in your game folder after installing BepInEx or SpaceWarp. More will be coming soon hopefully.
A demo of the custom planet mod is available now. It doesn't allow for creating your own planets, but showcases one I made myself. I hope allowing new planets shouldn't be too long, but I will be quite busy this next week.