According to UE5Coro Plugin, bEnableCppCoroutinesForEvaluation = true; can be added to .Build.cs file.
I have not personally tried it because I took a different approach of regenerating c++/WinRT header files via latest version of cppwinrt.exe which removed those incompatible headers. The version of c++/WinRT header files shipped with windows SDKs are outdated so by regenerating them for the target version of windows SKD helps make it compatible with c++20 and resolving several other compilation errors I encountered before. Hope this helps anyone who encounters similar issues in the future.