Check the answer in your forum post please.
I've added link to the FCOChangeStuff beta providing a setting + keybind there.
I'm not going to add this special settings to this group addon here as the only idea of this addon is notifying you.

I made a forum addon request on ESOUI, but I'm sharing it with authors of group addons...

So... I lead a lot of farming groups. Especially dolmen farming groups in Alik'r.
Apparently, a new trolling trend is to "ready check" randomly, and sometimes as much as possible.
It's maddening.

Since ZOS didn't give us the option of only allowing group leaders the privilege of doing ready checks, we could really use an addon that notified us in chat who started a "ready check", so we could then weed out the trolls and kick them.

Thanks CaptainBlagbird, will do so

@CaptainBlagbird - I've been using the version Baertram worked on for 6 days now, and it works wonderfully. Please post this version as an update.

IT'S WORKING!!!!!!!!
Thank you, Baertram.
@CaptainBlagbird - please consider uploading Baertram's version as an update.

Okay, last try. Should fix message if first group member is invited (only possible without @displayName though) and kick messages as well:
GroupNotifications_Baertram_Dragonhold

I can be happy with it working properly after the 2nd person joins. Because my main concern is with big groups. Like 12-24 members. So if it does in fact work correctly (joining and leaving messages) after a 2nd person joins, then that's not a huge problem in my opinion. I appreciate you looking further into it, though.

Yep, trying a fix like described but cannot get the displayname for that char then I guess.

Not working. Now I'm back to not receiving anything in chat about players joining or leaving group.

I've tested this with minimal addons enabled to check for conflicts. Conflicts isn't the issue.
(Enabled addons & libraries: Addon Selector, Group Notifications, Votan's Settings Menu, LibAddonMenu-2.0, LibDialog, LibMainMenu-2.0)

Edit/Update: Ahh, just saw your updated comment. So it's only going to work properly after the 2nd member joins?

Try if this works now. Some constants of ZOs for the group texts have changed:
GroupNotifications_Baertram_Dragonhold

I've also changed the texts to always show charactername link (@accountName) -> Except for group leader change as there is no easy parameter for this.

Edit:
Found out what is the problem with group join: ESO...

First event group member joined wil lfire with YOUIR OWN charactername only.
And all others with the other new members added.
So if you invite to a grup the first toon you won't see any message or your own character name only.
Cannot change this, this is ZOs made "logic"...

One would need to check if the group size is 2 and then implement another logic like "loop over all group members, strip the one which is the player and show the other's name then to chat" to fix this

I went through literally hundreds of strings on the github and I can't figure out how to make the messages give the @name and character name when people join or leave.

I assume something in these lines need to be changed:
But hell if I know.

And @Baertram... when I invite someone to the group, and they join, it tells me MY character has joined the group. lol.
Still not getting chat messages about players leaving the group.
So no, unfortunately, it's still not working as intended.

Try if this works please:
GroupNotifications Dragonhold Baertram

If not:
Disable ALL orher addons AND libraries and test again.
If still not: Maybe the server is not firing the events properly sometimes? Not sure. You could add some d(""got here 1") d("got here 2") entries in the functions and see how far the functions for the event group member joined or left will get (check the chat what get's posted).

And no:
Will not add the features requested below
At lrast the name or account shown should be an easy task to learn lua in this simple code and test if you can add it yourself maybe.
Learning info

Hint: You need SavedVariables to remember the settings for the name / account shown.

Doesn't seem to be working.
I'm definitely not getting messages in chat about players joining my group. I only see a message about them being invited.
May be an addon conflict, but can someone confirm whether or not they get messages that a player "has joined the group"?

Edit/Update: I'm definitely not getting messages about players joining or leaving groups.

I agree with JoyceKimberly and Majeure. I would love to be able to change the naming format (I'd prefer @UserID) and to see ready check information in chat.

Thank you for this wonderful addon.