Bluetracker
Tracks Blizzard employees across various accounts.
Tavern Brawl this week is... "Nefarian Rises!" (June 5th, 2019)
Chalkboard: "Join forces with a friend to take down Nefarian. Again. Anduin teams up with newcomer Morgl in this new cooperative Tavern Brawl!"
Format: Prebuilt Cooperative (use your stuff against a floating boss minion, not the other player (but it's OK to heal or buff OtherGuy's stuff))
Reward: a Classic pack
Wiki page about this one: https://hearthstone.gamepedia.com/Nefarian_Rises!
This is the third time we've had this brawl. The last time was January 2018; the Reddit thread for that time is here: https://www.reddit.com/r/hearthstone/comments/7soj0c/this_weeks_tavern_brawl_is_nefarian_rises/
Joemag
With few exceptions (Brawliseums and Single-Player brawls) most Tavern Brawls can be played with friends, and you still get a pack for winning!