> On most platforms it's quite easy to embed a browser in a frame

Citing other answer here "This is a common misconception among programmers, and is actually the opposite of the truth."

If platform is Windows then you need three different mechanisms for doing so, depends on OS version. And be ready to the fact that it can be no browser installed in standard way.

And if platform is Linux... Good luck with that in general... GTK may help here but be ready to GTK2/GTK3/GTK4 zoo. And sure you will not be happy with performance of the result.