Setting Google Tag Manager cookies with SameSite and Secure attributes

Chrome is already rolling out this change. You can set cookie flag in analytics.js or gtag.js for this to work, for example:

gtag('config', 'G-N2A3FMNDT5', {
  cookie_flags: 'max-age=7200;secure;samesite=none'
});

For more information and background, see this blog post: The New cookieFlags Setting In Google Analytics

For any of these warnings, if you are not responsible for the domain then you are not responsible for updating the cookies. The Google Tag Manager team will be responsible for updating the relevant code that sets the SameSite attributes for cookies from googletagmanager.com.

At this point, the warnings are purely informational and are not impacting functionality. Enforcing this behaviour in stable Chrome is not scheduled until M80, currently targeted for Feb 2020.