Xcode under macOS X 10.14 (Mojave)

When compiling for AI 23 under macOS X 10.14 (Mojave), are there any settings that need to be changed relative to earlier Xcode versions?

Using Xcode 9.4 and debugging AI 23, opening a new window causes all menu items to dim. Release versions work fine. This wasn't a problem under OS X 10.13 -- I could, of course, reformat my hard drive and go back to 10.13, but we'll all eventually have to move ahead again regardless.

Using Xcode 10, it immediately fails with the error "Could not create session." This is especially disappointing, since Xcode 10 in dark mode is very easy on the eyes, especially on older eyes with vision issues.

I should add that I'm using Hot Door CORE, which in turn uses the SDK. It's also very possible that one or both of these problems is related to having the XcodeLegacy script install multiple older Apple SDKs into the Xcode app. Does anybody else here use XcodeLegacy?

Any suggestions would be much appreciated!

-- Rick