The target architectures of this LFS edition are ARM64 (sometimes called AArch64) CPUs. On the other hand, the instructions in this book may work on 32-bit ARM CPUs with some modifications. To build a system that utilizes one of these alternative CPUs, the main prerequisite, in addition to those on the next page, is an existing Linux system such as an earlier LFS installation, Ubuntu, Red Hat/Fedora, SuSE, or other distribution that targets the architecture that you have.
The build results from this LFS edition is considered a “pure” 64-bit system. That is, it supports 64-bit executables only. Building a “multi-lib” system requires compiling many applications twice, once for a 32-bit system and once for a 64-bit system. This is not directly supported in LFS because it would interfere with the educational objective of providing the minimal instructions needed for a base Linux system. Some LFS/BLFS editors maintain a multilib fork of LFS, accessible at https://www.linuxfromscratch.org/~thomas/multilib/index.html. But the multilib edition is for x86_64, and multilib is an advanced topic anyway.