Its home and away between 2 teams.
In case of a tie between more than 2 teams, calculate as explained in the above posts.

This is something new I am seeing in the rules.
Also, it would be great if the CL rules (in-game) would be updated to include this.
Currently, it doesnt even say that tie-breaker is head-to-head rather than GD.
No wonder we have so may threads about this in the forum.