Steps to reproduce:

• have installed Qt, without cmake or ninja - neither from Qt installation, nor MSVC
• start QC with clean settings and a separately installed cmake in PATH
• link this QC with Qt
• create a project, use cmake as build tool

QC refuses to use the cmake that is set for the kit. (The kit needs to define a CMake tool to parse this project in issues pane)

Kits page:

• kits "appear" fine... they have the cmake set that had been found in PATH
• but they have a warning (cmake tool is unconfigured, cmake generator will be ignored)
• trying to modify the generator fails - no generator at all is listed
• checking the cmake settings page appears to be fine (cmake, version & help look like expected)

Explicitly adding a new cmake & assigning this to the kits works like charm - it also picks up a correct default generator.

Likely a result of QTCREATORBUG-31129.