Django runs on the server - it receives requests and returns responses.
What the software does on the requesting side is up to that software - Django has no control over that.
What that means is that:
- Yes, you can create a mobile app that communicates with a Django server.
- Yes, you can create a Django application that serves react (or some other JavaScript framework) to a mobile browser.
- Yes, Django can be coded to return HTML, XML, or JSON responses to requests. (Actually, it can pretty much return anything. Whether the client knows what to do with it is a different issue…)
<opinion> The choice between framework ABC and XYZ frequently depends upon considerations outside the technical merits of either ABC or XYZ. Many factors need to be taken into consideration, including the knowledge and experience of the people working on the project along with other environmental considerations. It’s rarely an issue of choosing A vs B because A is “better” than B based on some criteria. You’ll want to examine the entire environment in which your project is going to be developed.</opinion>
Some more of my opinions on this topic are discussed here: Should I use Django?, and here: Should I use Django for my project?.