Atheism is not a religion, but the lack of one. Libertarianism is not an ideology, but the lack of one.
Some libertarians just got seduced but the romanticism of socialist ideologies and they think they should have one.
Discussion
Sorry, but libertarianism IS an ideology.
Libertarism is a philosofy, there is no agenda, ideas or values to apply when tou are a libertarian https://thisvsthat.io/ideology-vs-philosophy
In the other hand, the philosofy os socialism is collectivism. The problem is that if you compare each other, they are not symetrical, while collectivism REQUIRES an agenda (comunism, socialism, fascism, democracy....) libertarism does not.
So there you go, if you are libertarian, you can't have an ideology. If don't have an ideolou, you are libertarian.