Rather than using a virtual machine to run the x86 version of Solaris, we'll use QEMU to emulate the actual SPARC hardware used by Sun machines back in the 90s. SPARC stands for Scalable Processor Architecture and is a RISC (reduced instruction set computing) design.
For Windows, you can download the latest binary from the QEMU site. I used the 20190218 build.
For macOS you can use homebrew to install it:
If you're running Linux, your distribution might have an older version of QEMU so you'll need to get the source and compile it. That goes a bit beyond this guide so take a look at the download page for more info.