could hold down the space bar until you are at the end, then save.
(Firefox) load everything > ctrl+a > right click > view source (have to wait a bit for that to work) > ctrl+a again > copy > paste into text document > save as > example.html
It is a truly insane workflow, as if you are trying to do something weird.
Better to just right click > take screenshot > whole page or use the cli https://firefox-source-docs.mozilla.org/devtools-user/taking...