I had the good fortune of encountering Randall Buth’s reading of 1st John today. He uses the reconstructed Imperial Koiné pronunciation, the system that represents how Hellenistic Greek most probably sounded in most places during the period of the Greek and Roman empires, more specifically between 200 BCE and 200 CE.
You can hear his reading here.

Now that ἡ ἡμέρα τῶν εὐχαριστιῶν has come and gone, it’s time to say καλὰ χριστούγεννα (Merry Christmas).