From Curseforge user loveyadeath - https://www.curseforge.com/wow/addons/who-taunted?comment=89:

Longtime fan of the addon, been using it for years on retail. Been actively playing Era since release.
Does NOT work correctly on Era. Tried v2.0 and v2.0.4.

The addon interface and options come up fine, but you never get a report or announce from Warrior Taunts or Mocking Blows.

Tested with another warrior.

Added a combat log that had everything turned on. No dice
Edited "My actions" combat log to show other player taunts. No dice

Tested in a 2 player PARTY and RAID (both warriors) simply taunting a mob back and forth.
Announce output was set to Party, Raid, and General. No dice.
PvP related toggles turned off.

Addon was not disabled during tests.

Never got a command prompt message like normal, nor any announces.
Addon is acting like it's not correctly reading the combat log. API issue?

Discord Lovepony#0374

... and that's why STA used names instead of IDs for Classic (=

https://www.curseforge.com/wow/addons/sta

So I take it back, not all tanks would have to have the add-on, but the add-on would have to be written to look for names instead of IDs for Classic Era.

Careful on things like "Growl" for Druids as they are also the same for Pet Taunts. I'd borrow heavily from STA -- the guy who made it stopped working on it about a year ago. Toss him a "thank you" credit for leaving his code permissively licensed. <3

Having worked with the Classic Era combat log for GogoWatch / RankSentinel... I can say that you can't really look at spell IDs on spells cast by other players. My suggestion would be to, sadly, close support for Classic Era.

The only way it could be achieved in Classic Era is if ever tank had the add-on running and the add-on shared information via comms. Just... really tedious to make it work in Classic Era.

FYI, I got a quick proof of concept on this working for Classic Era. Just needs a bit more testing before I send a PR. (=