To run openocd from System Workbench for STM32 on a external console, you need to indicate the openocd shared libraries location (eg. export LD_LIBRARY_PATH=~/Ac6/SystemWorkbench/plugins/fr.ac6.mcu.externaltools.openocd.linux64_18.104.22.168904120827/tools/openocd/bin/openocd/lib:$LD_LIBRARY_PATH) then you can run the openocd command.
Our version of OpenOCD was modified to be adapted to ST latest targets as early as possible. The generated configuration scripts are not compatible with other OpenOCD versions.
Sorry for late reply, hope it helps.