GitHub’s bug tracker was, a few years ago, my gold standard for bug trackers - precisely because it lacked the oceans of useless enterprise features two people on earth actually want but everyone has to suffer with, which Jira is thick with. Alas it seems they started adding them. IMO, it is a thing where less is more.
Nonetheless, I would vote for the leaner and corner of the options, which is decidedly Github’s issue tracker. -Tim -- http://timboudreau.com