enable proxy protocol for turn connections with tls

if a reverse proxy terminates the turns tls connection (TCP) on the tcp port 443, is it possible to use the proxy protocol to get the real ip of the incoming connection?

i believe this is essential if one watns to rate limit incoming connection attempts against ddos / brute forcing right ?

also, how do client authenticate to turn in jitsi ? i mean, can just anyone ask to open a webrtc connection to coturn -> jvb or is there some sort of client authentication going on via xmpp or so ?

thanks