defun eww-restore-history seems to need to start with a variation of
eww-setup-buffer:

(defun eww-restore-history (elem)
  (if (get-buffer "eww")
    (switch-to-buffer "eww")
   (switch-to-buffer (get-buffer-create "eww"))
   (remove-overlays)
   (eww-mode)
;; MISSING:
;; restore/retain values of:
;;   eww-history-position
;;   eww-history
   (setq-local eww-next-url nil)
   (setq-local eww-previous-url nil)
   (setq-local eww-up-url nil)
   (setq-local eww-home-url nil)
   (setq-local eww-start-url nil)
   (setq-local eww-contents-url nil))
  (let ((inhibit-read-only t))
   (erase-buffer)
    (insert (plist-get elem :text))
    (setq eww-current-source (plist-get elem :source))
    (setq eww-current-dom (plist-get elem :dom))
    (goto-char (plist-get elem :point))
    (setq eww-current-url (plist-get elem :url)
          eww-current-title (plist-get elem :title))
    (eww-update-header-line-format)))




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