Installing Foxy on a Windows 10 machine is largely a case of following the instructions on the ROS website: https://docs.ros.org/en/foxy/Installation/Windows-Install-Binary.html
However, a couple of fixes are required to get things completely working.
It is important to install the correct version of Qt; it is necessary to hunt around (and scroll down!) on the Qt website and to customise the installation to get things right.
At the end of the installation the ROS website indicates to source the install with:
call C:\dev\ros2\local_setup.bat
However, for my installation the correct command is:
call C:\dev\ros2_foxy\local_setup.bat
At this point, the talker and listener tutorial examples worked. But the turtlesim example (which uses Qt does not). It reports “Failed to load platform plugin Windows”. The following command fixed it:
C:\Qt\5.15.0\msvc2019_64\bin\windeployqt C:\dev\ros2_foxy\Lib\turtlesim\turtlesim_node.exe
After this the turtlesim and turtlesim_teleop tutorial also works correctly.