With a few managed services, you can create an end-to-end IoT scenario. Ingesting the data using MQTT, delivering it to a Knative serverless endpoint, storing it in a time-series database, and visualizing it. All with open source and still, managed for you.
Of course, I would encourage you to get everything deployed locally. Just to see that you can indeed self-host all of this. You can also try to swap out components and service offerings, as it is an open architecture.
Using the same mechanism, you could of course also push the data to another service. Or maybe enrich or pre-process it using a Knative serverless function. You could also build some application on top of the Timescale database, now that you have some data. Or if you like to work with SQL, create some fancy queries, and learn about the advanced features of TimescaleDB.