How to use 2 i2c channels on stm32f103c8t6 (other than pb6 & pb7) platformio framework arduino

Unfortunately, I cannot give you an answer to your actual question.

But I have noticed that your platformio.ini contains duplicate or contradictory entries.

bblanchon/ArduinoJson@^6.21.0
bblanchon/ArduinoJson@^6.21.0
khoih-prog/STM32_PWM @ ^1.0.1
khoih-prog/STM32_PWM @ 1.0.1

Please also note that the khoi-prog/STM32_PWM repository is archived and no longer maintained (see github.com/khoih-prog/STM32_PWM).

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