The following features were added:
Added support for NetworkLink refresh modes onInterval, onExpire (only through a NetworkLinkControl expire) and onStop. Includes support for viewboundScale, viewFormat, httpQuery.
Added partial support for NetworkLinkControl including minRefreshPeriod, cookie and expires. Network Link Control updates still aren’t supported.
Added support for a local StyleMap. The highlight style is still ignored.
Added support for root:// URLs for older documents.
Added more warnings for unsupported feature so you can know why something may not be displayed correctly.
These features will be in the Cesium 1.19 release on March 1. If you want to try them out early, they are in master as of this morning. Let me know if you run into any issues.