Symfony version(s) affected: 3.4.36

Description
Chrome is currently throwing a warning:

A cookie associated with a cross-site resource at was set without the SameSite attribute. A future release of Chrome will only deliver cookies with cross-site requests if they are set with SameSite=None and Secure.

How to reproduce

  session:
      # storage_id: app.dynamic.session.storage
      handler_id: ~
      name: "%session.name%"
      cookie_secure: true
      cookie_httponly: true
      cookie_lifetime: 2630000 # 1-Month
      cookie_samesite: strict

Add the cookie_samesite option. The value does not matter as adding the option results in

Unrecognized option "cookie_samesite" under "framework.session"

Possible Solution

Additional context

Symfony 3.4 LTS is still a maintained branch, SameSite is now going into affect in browsers with Chrome expected to deploy soon. I am currently trying to implement this

https://www.chromium.org/updates/same-site/incompatible-clients

which is supposed to help determine when SameSite is required. Without Symfony 3.4 LTS support, this isn't possible.

The application is being deployed to a Ubuntu 18.04 LTS server with PHP 7.4.2.