You can also look at the pkgsCross package set:
$ nix-build -A pkgsCross.
pkgsCross.aarch64-android-prebuilt pkgsCross.gnu32 pkgsCross.pogoplug4
pkgsCross.aarch64be-embedded pkgsCross.gnu64 pkgsCross.powernv
pkgsCross.aarch64-embedded pkgsCross.i686-embedded pkgsCross.ppc-embedded
pkgsCross.aarch64-multiplatform pkgsCross.iphone32 pkgsCross.ppcle-embedded
pkgsCross.aarch64-multiplatform-musl pkgsCross.iphone32-simulator pkgsCross.raspberryPi
pkgsCross.amd64-netbsd pkgsCross.iphone64 pkgsCross.riscv32
pkgsCross.arm-embedded pkgsCross.iphone64-simulator pkgsCross.riscv32-embedded
pkgsCross.armhf-embedded pkgsCross.mingw32 pkgsCross.riscv64
pkgsCross.armv7a-android-prebuilt pkgsCross.mingwW64 pkgsCross.riscv64-embedded
pkgsCross.armv7l-hf-multiplatform pkgsCross.msp430 pkgsCross.scaleway-c1
pkgsCross.avr pkgsCross.musl32 pkgsCross.sheevaplug
pkgsCross.ben-nanonote pkgsCross.musl64 pkgsCross.vc4
pkgsCross.fuloongminipc pkgsCross.muslpi pkgsCross.wasi32
pkgsCross.ghcjs pkgsCross.musl-power pkgsCross.x86_64-embedded