SteamFork is immutable so any changes may be lost, however it may be useful to update packages to work around a bug. To install packages locally temporarily:

• Log into desktop mode and make the filesystem writeable: sudo steamos-readonly disable
• Install or update the package: Ex. sudo pacman -Sy steamfork-customizations-jupiter

As cool as a new entry into the landscape is, this one still has the same filesystem limitations as SteamOS. That’s not necessarily a bad thing, but I do wonder how this one will meaningfully distinguish itself from the others.