As of mid-July 2020, the Chrome (and Chromium) stable release channel has started to disable cross-site cookies by default. Mozilla Firefox has pushed this change to their beta channel and will likely release it to the stable channel soon. This change affects any DHIS2 application running on a different domain than the DHIS2 server instance, including applications running on localhost in development. It does not affect cross-site API requests which use Basic or OAuth authentication headers, as those do not rely on cookies for authentication.
In 2019 we established a new application development paradigm with the App Platform. The Platform provides a unified framework for DHIS2 Web App development, so it is time to deprecate a few of our legacy libraries!