HSI is out of spec for reliable USB operation, even though it sometimes works. stm32-h103 board has an 8Mhz external crystal which should therefore be used for any USB work. Originally reported as https://github.com/libopencm3/libopencm3-examples/pull/192
Examples in these directories are not only for the board listed, they are simply preconfigured for those boards. If you do not find an example of the peripheral you want to use listed for your board, please look at the other boards. The differences between boards for the examples is normally only LEDs and buttons on different pins, and different memory sizes.