I see the same issue posted here and here. It seems that your linker is giving you the double-definition issue which means your .c files are somehow added/included multiple times by Arduino IDE. There hasn’t been such kind of issue reported for Arduino IDE until recently, maybe they changed some ways of inclusions. (Maybe try an older version to see if anything changes, 1.8.19 works fine with SquareLine Studio exports). A quick web-search about this kind of issue in Arduino IDE might help: c++ - Arduino IDE compiler error multiple definition - Stack Overflow