Just tried in QtCreator 4.10.0: disabled ClangCodeModel plugin (to avoid duplicate error messages), enabled LanguageClient and configured it for clangd. Everything works great (and extremely fast, compared to ClangCodeModel) except 2 significant problems:

• clangd sees my "includes", but not <includes> from include paths configured in CMakeLists; natural and expected.
• Don't know how to pass diagnostic flags to clangd (particularly, to disable its complaints about me using C++17 features). No clangd command-line options for that.

Do you guys consider moving from ClangCodeModel to LanguageClient? Especially now, when LanguageClient is out of experimental state. Should be able to use same configuration mechanics, probably. Or maybe there're some inherent drabacks with LSP?