On many distros, getting multilib support is very straight forward. There exists a guide that can act as a replacement for LFS: compiling and configuring a system that can boot, run, and compile software; and also have that same ability with 32-bit. It acts to form the basis that will allow you to follow any of the instructions laid out in the Steam and Wine chapters.
Such a guide is maintained by Thomas Trepl at https://www.linuxfromscratch.org/~thomas/multilib-m32. This only covers installing 32-bit support along with 64-bit. If you want x32-bit support, which is not needed for this book, follow https://www.linuxfromscratch.org/~thomas/multilib.
You can render MLFS if you wish.
First, install git-2.48.1, then clone the LFS repo and switch to
the multilib branch:
git clone https://git.linuxfromscratch.org/lfs.git mlfs && cd mlfs && git checkout multilib
Now inspect the INSTALL file to check
for the needed dependencies in order to render the book. Once you
have ensured you have installed everything, render the book:
make -j1 ARCH=ml_32
The rendered files will be in ~/public_html/lfs-book.
The same principles of compiling for 32-bit in that book will also apply to this book as well. If you haven't already, read Important Information to check what basic principles still apply in this book when targeting 32-bit.
Furthermore, read Which Instructions to Follow to find out which instructions to follow.