I first encountered this when the machine auto-upgraded Xcode command line tools and broke the C compiler. Searching for arm64e.x1 led to this interesting article about the new architecture (from the perspective of the compiler and the linker). It’s especially interesting that this introduces new instructions and reuses the existing tooling for multi-architecture binaries (PowerPC + Intel, Intel + ARM64, ARM64 + ARM64e etc).
I found this article genuinely interesting despite having telltale signs of AI writing.