I do not really use Foundry anymore and was really just holding this until it was implemented into Foundry natively. It's a very low effort feature that is important to users and there is realistically no reason it's not already a native feature.
I have created a ticket on the Foundry Repo, which you can find here: foundryvtt/foundryvtt#11132
The more tracking that post gets, the more likely it will be added.
Shows an average of a players latency in the player window.
Foundry Link:
https://foundryvtt.com/packages/user-latency
Foundry Hub: