Libra doesn't have any competitors because it doesn't exist yet. And when it finally comes to life, it's going to be an interesting event to follow because they will definitely exclude certain countries from their network. It's a business at the end of the day, and they have to abide by the regulations per the country they plan to operate in.

Tether is somewhat comparable in the sense that it holds a basket of assets which their tokens are *supposedly* backed by. Tether however can't prevent you from transacting in any shape or form because it's built on decentralized protocols (e.g. Bitcoin, Ethereum). Facebook will be able to censor transactions and put a hold on your balances.