How to choose variant.h for STM32F030C8T6

When I select “variant”: “EEXTR_F030_V1” for stm32f030c8t6 I get usb related errors EEXTR_F030_V1_errors -
If I set “variant”: “stm32f0” I get errors related to variants.h variantsh_error -
What do I need to fix in the json file of the board or which variant should I choose?

Duplicate of How to config STM32F030C6T6 support arduino framework?

See GitHub - maxgerhardt/pio-f030-test