There is a well-populated operating systems development IRC channel on Freenode at #osdev. Several regular contributors to the OSDev.org wiki and forums are usually present in the channel.
The easiest way to connect to the channel without an IRC client is through Freenode's AJAX IRC web client.
The OSDev Discord isn't as active as the IRC, but nevertheless you can join at https://discord.gg/aJPTY8Y. The server is owned by osdever (username osdeverr on forums) and is administered by obiwac, Geri, k1-801 (not on the forums), no92 and omarx024.