How can I Ctrl + Alt + Delete on Win 10 using a Mac keyboard?

On Macs, the Command key is physically located where our fingers are used to the Alt key location, at least in the US. But, it's the Option key that sends the same keycode. So... you should be able to use Ctrl-Opt-Delete, except I'm not 100% sure that the Mac's delete key corresponds to the Windows one.

Since you want to use your Mac keyboard permanently with a PC (which is exactly what I do, using a USB switch to go between the Mac and PC), you REALLY should download Keytweak for Windows (available at https://keytweak.en.softonic.com/ and many other popular download sites), run it and map your Mac keys. Here's a pic of my mapping to get you started, although you can't see a couple others that I have mapped (UI won't scroll), but you'll get the idea.

Not sure if the question was ever answered, but I solved the issue on my magic keyboard. I discovered a second delete button -- not the larger delete button that has the word "delete" (next to the + button), but instead the delete button to the left of the "end" button and directly beneath the fn button. This second delete button has a little x on it as well. I'd never seen it before but just stumbled on it.

Take away: I hit this particular CTRL-ALT-DELETE combination and it successfully took me to my work windows login page. Hopefully this helps someone who's been struggling with Google or trying different combinations involving the apple command button, etc.