В этом документе пишут:
https://www.st.com/resource/en/reference_manual/rm0008-stm32f101xx-stm32f102xx-stm32f103xx-stm32f105xx-and-stm32f107xx-advanced-armbased-32bit-mcus-stmicroelectronics.pdf
Здесь в "Table 3. STM32F103xx family"
https://www.st.com/resource/en/datasheet/stm32f103c8.pdf
DAC есть только в High-density devices от 256 KB Flash