There is a guide on how to set up LineageOS for libvirt (i.e. QEMU) [1], but there exist no prebuilt images at this point in time.
I can't even fathom what the build system is doing in order to require this amount of storage.
A large number of 17 year old repositories, prebuilt toolchains, and the fact that you otherwise have every little bit of source code, intermediary results, and output to create a full operating system all in the same place.
As for the memory, the very first step (that basically already is the benchmark for the most memory usage) is loading the entire build tree and generating build steps. Yes, that takes 32GB of RAM, if not 64GB nowadays.