As of this latest release, Cirrus has launched many new features that may not be compatible with all browsers, especially older ones.
For instance, Cirrus no longer uses vendor prefixes in styles that are known to have some compatibility issues except for a few parts. Cirrus also supports new features such as CSS grid, object fit, and sticky positioning which is not yet supported on all browsers.
In short, Cirrus supports all the latest supported browsers with only partial support for Internet Explorer. Take it from me, I wouldn't advise using that browser anymore.