This sounds similar to a modular monolith design. But you have to be careful not to directly import things between apps and especially not to make foreign keys between the models of different apps. We ended up doing that and just wishing it was one big app.

Modular monolith is a good idea and if you want to do it in Django then make small apps that just expose services to each other (ie. high-level business functions). Then have a completely separate app just for the UI that uses those services.