Libertarians - at least the ones over at Volokh - have had strong but mixed opinions about President Trump. They have largely regarded his combative, insulting comments as unimportant, in contrast to the supporters who like his fighting call-'em-out spirit and whose opponents who believe that insulting them is some new unholy degradation of political discourse. To the libertarian, these are often just noise. They have liked his effort to reduce regulations and get America out of as many wars as possible. They have disliked his executive orders (even when they agreed with the substance sometimes) and attempts to circumvent decisions by the other two branches of government.
I went looking for a strong libertarian case for impeachment. While they are much in favor of smacking down all politicians attempting to overstep their authority, they also dislike disruption of the normal order of things for purely partisan reasons. They don't dislike it as much as Burkean conservatives, but they dislike it. With regard to the previous impeachment, for example, there was something of a consensus that it should be allowed to go forward, and the reasons against that would be bad precedents, but on the merits, it was unlikely that Trump should or would be removed from office. The author I am about to mention would fall into this camp. Please! Bet eager to impeach presidents, because there hasn't been enough of that and they have run amok! But the case you are bringing against this president does not pass muster.
This particular libertarian, Michael Stokes Paulsen, has a string of associations which would likely be admired by conservatives as well as libertarians in normal times: co-director of the Pro-Life Advocacy Center, Witherspoon Institute (including a humorous but serious essay "Everything You Need to Know About Constitutional Law."), Pepperdine University, University of St. Thomas, Federalist Society, writing for Law & Liberty, Public Discourse, Reason, National Review, and I stopped looking. I will acknowledge, however, that while he seems to have started out as mildly pro-Trump or at least neutral, he gradually decided that the POTUS was no real representative of libertarians or even conservatives, however good a job he did at upending liberals and statists. So by the time he got to writing this week for The Bulwark, he was not well-disposed toward Mr. Trump and that may affect his viewpoint, particularly his tone. Yet he is definitely one against whom the recent charges that I have seen on a dozen conservative sites, that those who have "turned on*" Trump are trying to curry favor with the establishment, are cowards, or are refusing to look at the evidence cannot be reasonably brought. If he is wrong, it is at least not for those reasons.
You will perhaps find this inflammatory, The Constitutional and Moral Imperative of Impeachment, to which Paulsen might reply "We Didn't Start The fire." If you want a more thorough libertarian overview, The Volokh Conspiracy is your usual first stop.