JustEat (European food delivery app) did this right. They acquired a bunch of companies, pyszne.pl, takeout.com, whatever the German one was called, and just replaced all their apps with the one they already had. The branding stayed the same, the Polish app for example is still called pyszne.pl and the JustEat branding is completely absent here, but all of these apps have the same UI and use the same backend. You can see this very clearly if you go to another country and open your local app, it's just going to work.