"Could not locate device support files" with Xcode version 11.3.1 and iOS 13.5.1
This Stack Overflow question answers this. You need to copy and paste over the SDK for the iOS version that your phone runs on into this file location: &lt;where ever xcode is located on your machine&gt;/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport.
After downloading the appropriate file, you can go to Terminal and paste this:
unzip /Users/yourname/Downloads/13.5.zip
cp ~/Users/yourname/Downloads/13.5 ~/Users/yourname/location/of/Xcode.app/Contents/Developer/Platforms/iPhoneOS.plaform/DeviceSupport

Here's the link to the SDK for iOS version 13.5 (includes 13.5.1) that you need to paste over.
You can also update to Catalina to get a later version of Xcode, but I don't recommend it if this is the only thing you're doing it for.
Apple no longer allows you to downgrade your iOS version, so that option is now, sadly, null.
Edit: I just wanted to make it clear that this approach works for all versions of iOS, not just 13.5. Just download the your system version's corresponding file and paste it into the location mentioned before. Make sure to unzip the file before pasting it though.