I found this bug tapping the help button in Obsidian, but it applies to help.obsidian.md in general.
If I try to go to the help site on my iPad I get a black page with “Obisidian Publish” as the page title in the tab. If I switch the default browser to Firefox, everything works just fine, but I cannot find a way to show the help site at all in Safari. It works fine on my iPhone, by the way, so this seems specific to Safari on iPadOS.