IA Ignition does have a historian module that, in practice, I've had a difficult time working with. Ignition is an all-in-one solution from the edge to visualizations to historization and it has a relatively shallow learning curve. Many small-to-medium size manufacturers get a lot of value from it. OT professionals with little IT knowledge can thrive working with Ignition. You have to be smart about the decisions that are made as these deployments scale though, because bottlenecks eventually appear (my understanding is this is because it has a layer of java abstraction between the application and the host). So the journey of an Ignition deployment typically goes from a single gateway PoC doing everything to numerous gateways that do a subset of tasks each (edge data collection, visualization, historization, gateway area network management, etc). Over time I think we'll see more and more brownfield cases where platforms like the UMH take on a central/UNS-supporting role complimenting legacy, distributed Ignition deployments. We may also see the opposite, where Ignition does the visualizations like @Denis demonstrated and the UMH runs on many nodes closer to the edge and does the data collection.

I think you summarized bith approaches quite well. We thing the best way to combine Ignition and UMH is to do it how Denis showed it. If the other way works with just ignition, and there are no challenges with it, then the UMH does not provide much value add. Only when one realizes that the existing connectors and Ignition approach are not scalable, it makes sense to use the UMH.