The installation guide states:
wkhtmltopdf
is not installed through pip and must be installed manually in
version \0.12.5 for it to support headers and
footers. See our \wiki for more
details on the various versions.
(from \https://www.odoo.com/documentation/14.0/setup/install.html#prepare )
Ray, you may want to change the misleading title, I think you mean wkhtmltopdf, not Webkit :-)
... and, IIRC, wkhtmltopdf was never installable through pip, it had always to be installed manually.