Just realized by going through the forms of an actual project that the font of TLabel was changed.
In the original app neither style nor anything else concerning fonts was changed but any added label uses a different font (style) now.
Screenshots show the difference
Delphi 10.0 New Form with Label (Android)
Delphi 10.0 App Base Form with new Label (Android)
Delphi 10.1 App Base Form with Label (Android)
(to be continued … may be)