How to disable event notifications for group I'm not in?

I used to be a part of the "Tomb Raider Multiplayer Madness" Steam Group. They have regular weekly events. I became annoyed with the event notifications, so I thought leaving the group would cease them. I left the group. I'm still getting event notifications from the group. How do I stop the event notifications?

Solution 1:

Apparently, with the new "Explore your Queue", when you choose to follow the game, it adds that game to your groups and it can only be removed through the community hub of that game.

Do not follow games if you do not want notifications from that game.

Solution 2:

In your friends list, there's two tabs - one for friends, another for groups. Click the groups tab, and you'll likely see the tomb raider group there. You can remove yourself from there.

If that doesn't work, go to the Tomb Raider community hub. There should be an unfollow button on the page:

Between these two locations, you're guaranteed to never be notified of any Tomb Raider events ever again.