Proteus (closed source, paid) has a whole range of microcontrollers, and I’ve found it to be great (pirated it). There is also Simulide (open source) with a more limited bunch of microcontrollers which I havent used much but was pretty nice.

Both allow you to attach your MCU to external circuits with Proteus in particularly having a wide range of components you can use. They also have tools for measuring and oscilloscopes, etc.