32 bit systems are limited to max 4gb RAM, why would you install it? Most these mini pc's have 8-16-32gb ram. You can make a usb stick with windows 10 32/64 and choose 32 bit when you install it. Use windows 10 Media Creation Tool to make the usb.
I'd like to eat my words. Yes, you can install 32-bit Windows 10 on Beelink SER5 5500U, but it is recommended to use the 64-bit version for better performance and compatibility with modern software.