Hi.
I first used the Digistump AVR boards manager:
https://raw.githubusercontent.com/ArminJo/DigistumpArduino/master/package_digistump_index.json
and loaded the board "Digispark (Default - 16.5 mhz)".
Is that the core you refer to? I explored the discussions about this term "core". Not an area for new players I feel. The expert users admit it's an ambiguous term.
Board appears in device manager as :
