Hi all,
going through the documents again at this point, there still does not seem to be an option to disable the “View this in your browser” link for emails sent from ERPNext.
There is the workaround by changing frappe/templates/emails/print_link.html (see Remove View this in your browser in quote), but this would change the code base and is not optimal.
As I could not find a github issue for this feature request, I have added one: [Feature request]Option to disable email link "View this in your browser" · Issue #5539 · frappe/frappe · GitHub