The Windows copy ships with a 32-bit version. I haven't set up the manifest here on itch for it to launch properly through the client, so your best bet would be to grab the installer EXE. It should have the option to install the 32-bit version.
For Linux, unless you're on a 32-bit distro that has Flare packaged, you'll need to build it yourself. Instructions for doing so are here: https://github.com/flareteam/flare-engine/blob/master/INSTALL.engine.md