"Notes from the Underground" takes place a few weeks after season 6, it was released in 2002 and it's one of the old Dark Horse comics that aren't canon (though they tried not to contradict canon). Although the chronology is very fuzzy since Angel and Cordelia appear in it, which means it should happen before AtS season 3 finale, since he's not at the bottom of the sea and she's not on the Higher Plane. Faith is in it as well (released from jail for a day) and she goes with Angel to Sunnydale to help. They managed to somehow get most of the characters from both shows in there in some form or another, even if it's a flashback or a vision or a mention, probably because the 4th part was some kind of anniversary issue. Even some people you really wouldn't expect were in it, like
It's a nice little comic (especially for character interaction), except that it's a bit too expositiony (it's like they wrote if for someone who doesn't know the shows well so they introduced every character and retold a bunch of stuff) and the colorist didn't get the job done well - Dawn's hair looks red and Buffy's eyes are blue.