Fetch does not send Cookies with SameSite=None and Secure to an HTTPS page

I have the following setup:

• My backend server running on https://backend.com/api
• My web app running on http://127.0.0.1/login
• The browser has a Cookie:
  • SameSite: none
  • Secure
  • Domain: backend.com
  • Path: /
  • And a value of course

When trying to make a request to the backend from my web app no cookies are sent.

let response = await fetch(url, {
    credentials: 'include',
    method: 'POST',
})

What am I missing?

The following thread has given me a hint, which I am not sure if is the problem: HTTP pages are removing my secure cookies

When the user tried to visit an HTTPS site from an HTTP one, their request would start as an HTTP