How to get YouTube sub count onto a Roblox game?

You can easily do that using youtube's api and roblox's HttpService

Here's an example:

local HS = game:GetService"HttpService"
local ApiKey = "your youtube api key here"

while wait(2) do
	local resp = HS:GetAsync("https://www.googleapis.com/youtube/v3/channels?part=statistics&id=UC-lHJZR3Gqxm24_Vd_AJ5Yw&key=" .. ApiKey, true)
	resp = HS:JSONDecode(resp)

	textlabel.Text = resp.items[1].statistics.subscriberCount
end

here's an example response