It hasn't been properly rolled out yet, but I've figured out how it can be done (and it's really easy!). Not sure if this has been fully rolled out inside excel yet, I'm using excel 365 and it's working for me.
In excel, do Get Data -> Other Sources -> Blank Query.
The first line of your query needs to be:
=PowerPlatform.Dataflows(null)
If you've ingested a dataflow into Power BI before, this navigation will start to look very familiar. You'll need to sign in with your organisational account, and then you should see a table in the previous window show the records "Workspaces" and "Environments". Click "Workspaces", then under the "Data" field select "Folder" and it will drill down to the next level. You can keep navigating down in the same way, but I find the easiest way to continue is to then click the Navigation Cog in the "Applied Steps" box and navigate exactly the same way that you would do in Power BI.
Congratulations! You've just connected Excel Power Query to your Power BI Dataflow! You can now interact with the dataflow in PQ exactly as you would any other source, and once you're done you can Load your data directly into your data model or a tab as usual.
