FluentHMI-Studio (35 stars): a free drag-and-drop HMI builder for Modbus and MQTT on Qt 6.
FluentHMI-Studio is a C++ and Qt 6 desktop app where you drag widgets onto a screen and bind them to serial, TCP or MQTT data, including Modbus RTU and TCP. It exports a standalone operator app in under a second with no compiler. A free way to mock up an operator screen for a skid or test bench.
For controls techs and hardware engineers building quick operator screens.