Not sure how I missed this, or how long it’s been there, but when in Safari on iOS you can screenshot a webpage and when the edit-view comes up you can select "Full Page’ and save the entire page.
New with iOS/iPadOS 13.
you, it’s very handy. I found that sometimes it doesn’t capture the whole page but only 80-90% of it. But it might be a problem with the page underlying html, not iOS fault.