Had the same issue and as suggested before in other comments, hit Shift, Command and the number 2 to open Devices and Simulators. In my case, my phone was IOS 14.6 and xcode was at 12.2 - there were Red errors clearly telling me what to do - it said my device (iphone) was one of 5 or 6 listed that were running IOS 14.6 and I needed to update to a version of Xcode that supports IOS 14.6. That said, turned out my older macbook pro could not be updated to the version I needed so I ended up getting a newer macbook pro. So it is possible to be in a situation when your macbook cannot support what you need. Everything was fine until I got the bright idea to update my phone that it became uncompatible.

Got this from another forum post and worked for me. Under build settings make sure the IOS Deployment Target matches the IOS version on your phone. If you have an older iphone that cannot be updated anymore, this might not work. I have an app where under Build Settings shows the Project and two Targets, I matched both these to my IOS version of 15.0 and the error went away and the build completed.

Thanks this worked for me. I opened another project and xcode did not crash.

UPDATE to my previous post. Reopening another post did allow xcode to open without crashing; however, my current project failed to open and did in fact crash xcode. This worked for me: deleted my project workspace, deleted my podfile.lock and Pods folder. You may also simply rename at the terminal with: > mv yourprojectfile.workspace to yourprojectfile.workspace.bak or any other name. Do the same for the folder. reinstalled my pods via > pod install. So the crash was due to my project. Before you go nuts trying to fix xcode, it may be a good idea to test if it an xcode problem or a project problem. So thanks for your tip: by opening another project, it led me to think this issue was my current project.