The Super User question guidelines say that questions related to computer hardware are on topic, so I would expect a problem replacing a smartphone's LCD and digitizer would be on topic, but the guidelines also say cell phone related questions are off topic, so even though this question would deal with hardware, would it still make the question off-topic?
From the guidlelines:
Super User is for computer enthusiasts and power users. If you have a question about …
computer hardware,
computer software, or
personal and home computer networking
and it is not about …
programming and software development,
video games or consoles,
websites or web services like Facebook, Twitter, and WordPress,
electronic devices, media players, cell phones or smart phones, except insofar as they interface with your computer,
issues specific to corporate IT support and networks,
asking for a product, service or learning material recommendation,
… then you’re in the right place to ask your question!