The Front Panel module has been moved from UI pack to MicroEJ Architecture. The new Front Panel module has been designed to be MicroUI-less compatible. A platform can use the Front Panel without using MicroUI API (to show a splash screen when the application boots, blink a LED without using MicroUI Led API, etc.).
UI pack < 12.x contains the old Front Panel module
UI pack >= 12.x has an extension of Front Panel module for MicroUI
MicroEJ Architecture < 7.11 has not the Front Panel module
MicroEJ Architecture >= 7.12 has the new Front Panel module
The Front Panel module visible at the root of the tree is the new Front Panel module in the MicroEJ Architecture 7.12.1. The Front Panel module visible in the UI group is the old Front Panel module included in UI pack 11.0.0.
You can keep using the old Front Panel module (included in the UI pack). Install MicroEJ Architecture 7.12.1 and UI pack 11.0.0. Uncheck the new Front Panel module and check the UI Front Panel module.
If you check the new Front Panel module when the UI pack 11.0.0 is installed, an error is thrown: the UI pack 11.0.0 is not compatible with the new Front Panel module.
If you install the UI pack 12.x, you have to migrate your Front Panel project. Indeed, the new UI pack contains only an extension of the new Front Panel module for MicroUI. The FP file format and FP project format have also changed. New Front Panel module is explained here: https://docs.microej.com/en/latest/PlatformDeveloperGuide/frontpanel.html.
I disabled the top level Front Panel module and enabled the UI/Front Panel and now my platform builds without errors.
I will continue with the legacy Front Panel module using UI Pack 11.
I will have a look to migrate to the new Front Panel later.