Ultimaker Cura uses OpenGL libraries. A recent update of Mac OS to version 'Big Sur OS' in combination with new Apple M1 processing chips has introduced incompatibilities between the OpenGL libraries used, and the latest firmware used by the Macs.
You can read more about the Apple M1 chip on their website.
This means that Ultimaker Cura is currently not fully supported on new Macs containing the M1 chip, resulting in visual and interface-related glitches. Please bear with us while we look into fixing this in an upcoming Ultimaker Cura version.