Comment 2 for bug 1703419

In that case, the FAQ should be updated:

https://inkscape.org/en/learn/faq/#how-create-custom-palettes-and-how-save-colors-future-use

"To install a palette, copy the .gpl file to the /palettes directory in your Inkscape installation (on Ubuntu: /usr/share/palettes/, on Windows: (\share)\palettes directory in Inksape installation directory)."