stm32flash is an alternative to STM32 Flash loader demonstrator (FLASHER-STM32) for Linux users, there are some pitfalls, though.
No Recent Releases #
Although the development is still active, latest release at the time of writing is 0.5, which does not fully compatible with some of the new chips. In my case, I would have to clone the repository and compile from source in order to have those chip supported.
CH340/CH341 #
According to AN2606, flashing through UART requires parity support. Linux driver for CH340/CH341 does not have it until 4.10. (Kernel version of Debian Stretch is 4.9 by default.)