I am designing a redundant system with at least 2 STM32 that i would like to program and debug with JTAG chaining. I have an Amontec JTAGKEY-2 (works in ftdi) and my targets are STM32F405RG. I posted details about the question in stackoverflow .
Most debuggers will be able to connect to any of a JTAG device inh a JTAG chain, one target at a time. I do not know of a debugger capable of connecting to multiple targets at the same time. Maybe the expensive ones, like Segger,
