It is important you prepare yourself and be ready for this change.
What can you do? While you are testing and evaluating the potential impact this new Chrome release may have (for that you can download the beta version here https://cloud.google.com/chrome-enterprise/browser/download/?h1=en#chrome-browser-beta), you can set the SameSite flag (see https://www.chromium.org/administrators/policy-list-3/cookie-legacy-samesite-policies) using Group Policy; remember as a GPO is setting registry keys and values, this can be deployed either way with Group Policy in case of your devices are domain joined, SCCM if you use it and some of your devices are managed by SCCM and not domain joined or Intune
What could be broken? The following and not exhausted list shows you what could be the issues you will be facing if you are not ready: