That news about (temporary) break in Arduino support for the STM32F103 completely passed me by.
I have one production project, a satellite dot matrix clock, which uses an STM32F103 (Bluepill) and 4 unused ones waiting for a suitable project - they were so cheap I bought 5). For the satellite clock, the additional serial ports and the builtin RTC with minimal standby power consumption were useful.
However, there is a bit of a learning curve and the initial set up is not completely trivial. I seem to remember having to register at a site to download a bootloader and some interface software. I never got to understand the architecture to the same extent as with the AVR architecture (direct manipulation of hardware features such as timers, ADC etc.) and in the meantime. the cheap and powerful ESP devices have come along.