So, after trying out a few things I actually ended up with a solution to my specific problem. As pointed out by @JRR, the pipeline argument does not work with LidR LAS objects as specify it directly in the function but it just does not work. However, you can still use different transformation pipelines, they just need to be the default option with st_transform. So when calling sf::st_transform(las, crs = 25832), it uses the method that is at the first place when looking at the options through options <- sf_proj_pipelines(source_crs = "EPSG:31468", target_crs = "EPSG:25832"). In my case it is a transformation that makes use of an NTv2 file, which can only be accessed through the connection to the network with sf_proj_network(enable = T), however I tested a few times and the only way I could use it with the Lascatalog processing engine was to actually put the file itself in the directory of st_proj_search_paths().