Buggy update process
Tried three times to update by responding to the dialog about the 4.0.2 update that came up in the previous version (was it 4.0.1.2?). MU4 crashed and disappeared each time during the installation, though seemingly at different stages in the process.
So I uninstalled MU4, restarted as requested (because it was unable to close some Musescore-related service), and then launched Muse Hub to download Musescore. This resulted in a download of 4.0.1.2 (or whatever the number was of the version I had just uninstalled). When it launched, again it displayed the dialog about the update to 4.0.2. Again I clicked the button. This time it worked, but I got a message during the installation process that it couldn't close Musescore 4 and I should do it. I looked in the Task List for an instance of Musescore 4 and there was none. So I just continued. At the conclusion of the installation I left the box checked to launch Musescore 4 and clicked . 4.0.2 got launched and appeared operational. But then I noticed a dialog saying I needed to restart my computer to complete the installation.
Whew. Bumpy!
I guess it's been installed successfully. I'll find out.