I understand hydrogen can be generated from steam-methane reforming or from electrolysis of water and then cooled to liquid through a series of cryogenic coolers. For steam reforming, the hydrogen needs to be separated by pressure swing adsorption, through a membrane, or through liquefaction since it has such a low boiling point of -252.9C. Oxygen just needs to be separated from air through cryogenic means with a boiling point of -183C compared to nitrogen's -195.8C.
I assume this is done on site, but which methods are actually practiced?
This answer talks about the supplier, but doesn't go into the details of how it's produced (steam-reforming, electrolysis, etc.)