It is not available as of yet but soon it will be. Lets just wait till then. I think it will have an impact on prices of alts since they are already bleeding in todays market as of 2019, but this will bring new competition to BTC. Lets see what happens with the price of BTC.
In connection with btc, libra will have less impact since it doesn't have any direct relation to bitcoin but with the market itself. Like for example, Bakkt, people blame the launch of bakkt after bitcoin downed a thousand dollars right after it introduced to the market, why? because it is hyped by many which has been taken by the whales for granted. New currency does not have direct affect on prices, speculation does. 