I am libertarian-ish, but generally don't like all the loud libertarian nuts (I register Dem and vote Dem because the things I care about aren't represented anywhere on the ballot anymore).
For me, it comes to a very simple economics truism: Governments are pretty damn inefficient and tend to waste a lot of money because of the process and bureaucracy. Markets on the other hand, tend to be really efficient at allocating capital when left alone. The times a government should step in is when the market has created a form of externality that breaks things. The old economics example is the people downstream from a chemical plant are paying the price for the plant's pollution.
From a libertarian lens:
The government should negotiate SPH b.c. it's obvious that markets failed and we'd all be better off (spend less money) if everyone had healthcare.
The government should stay out of people's bedrooms and love lives, it has no business there.
The government should use UBI and then eliminate every other deduction, and tax break, and subsidy (Social Sec, . The office running UBI could be one guy sending checks out once a month (exaggerated obvi)
Unfortunately the things I'd like to see from a libertarian don't actually show up.