No longer actively supporting React version < 16.3. The minimum supported version of React is now 16.3. Discussion can be found here
If you are using the material-ui 4 theme, @material-ui/core and @material-ui/icons packages should be updated to the latest versions. The minimum versions supported for @material-ui/core and @material-ui/icons are 4.12.0 and 4.11.1 respectively. This change is required for support for the material-ui version 5 theme