Abortion is a fundamental position for libertarianism, just as being pro-life is for conservatives.
Pro-life libertarians are a minority, and they support and promote an ism that is pro-abortion, the old Ted Kennedy position of being "personally pro-life" but supporting and promoting the democrat party.
Rand Paul claims to be pro-life, but he isn’t officially a libertarian. He’s hard to figure out.
I have heard of quasi-choice libertarians.
I’ve heard of rape/incest/life of mother ‘pro-life’ libertarians.
Mostly, though, and exactly as you say, libertarians are pro-abortion.
HOW can they possibly object to any homicide if they don’t object to every homicide?