Only Macintosh shown on Startup Manager after Windows 10 32-bit Boot Camp install
Solution 1:
32-bit versions of Windows 10 are not supported on any Mac model. You need to install the 64-bit version.
From Apple KB: How to install Windows using Boot Camp
Before you begin, make sure you have everything you need:
- An Intel-based Mac
- A Microsoft Windows installation media or disk image (ISO) containing a 64-bit version of Microsoft Windows 8 or later
See this list for which Mac models support Windows 10.