I have a framework for developing OPC UA servers at bazza2jw/OpcServant on Github.
It intended to fit in at SCADA levels 0 and 1.
It provides a C++ framework to develop OPC UA servers with desktop and web configuration and display interfaces. The intended target hardware is SBCs running Linux like the Raspberry Pi.
It is based on wxWidgets, Wt, open62541cpp
The framework includes reporting, tables, graphs and statistics (desktop and web interface).
There is MQTT support and SQL logging support. Using Node Red (and report generator like Crystal Reports), results in a rapid to develop bespoke SCADA systems with not much work (I hope).
Hopefully useful if only as examples of how to use the above 3rd party libraries.