This is an experimental LFS fork for 64-bit little endian MIPS (mips64el) CPUs. Specifically, The instructions are only tested on a Loongson 3A4000 CPU. On the other hand, the instructions in this book should also work, with other mips64el CPUs. To build a system that utilizes one of these 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 default 64-bit build that results from LFS 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 instructions needed for a straightforward base Linux system. Some LFS/BLFS editors maintain a fork of LFS for multilib, which is accessible at https://www.linuxfromscratch.org/~thomas/multilib/index.html. But the fork is for x86_64, and anyway multilib is an advanced topic.