What is necessary to run Linux ARM64 binaries on Android ARM64?
To run conda-forge arm64 Linux binaries on Android in termux requires proot-distro because the ABIs are slightly different FWIU.
What is necessary to run Android ARM64 binaries on Linux ARM64?
Android Studio, LineageOS or BlissOS's outdated Android containers, a runtime like vinegarhq/sober that emulates just enough of Android.
An Android binary that makes Linux compatible syscalls only (that doesn't require Android libraries that aren't compiled for Linux) won't work will it?
A fully statically compiled Linux ARM64 binary which only interacts with the kernel through syscalls should run no problem on ARM64 Android. From the kernel's perspective, there is no difference between a "Linux binary" and an "Android binary" because the kernel in Android is Linux.
Most programs want to interact with various system libraries and system services though. Android and your typical desktop Linux system share pretty much nothing aside from the kernel.