Hi!
Thanks for the mod!
There's a small problem, it's described here: https://mods.factorio.com/mod/LiquidRocketFuel/discussion/6951dbf28f410663227deec6
Please make a change to the code to avoid the error.
Only in your mod is the code in the "functions.lua" file, line 89. Here is the full "edited" version:

function find_planets_missing_rocket_parts()
    if settings.startup["external-rocket-parts-diversity-setting"].value ~= "none" then
        planet_list = {}
        for _, planet in pairs(data.raw["planet"]) do
            if not data.raw["planet"][planet.name].hidden then
                if data.raw.recipe["rocket-part-ext-" .. planet.name] == nil then
                    table.insert(planet_list, planet.name)
                end
            end
        end
        return planet_list
    end
end

thanks for this fix, added it to the latest version