There is no Pi 4 image to download from https://voidlinux.org/download/.
Turns out there is (experimental) support of EFI boot for Raspberry Pi 4, meaning we could boot operating systems (including Linux, Windows, etc.) using EFI just like we do on x86 PC. At the same time, mainline Linux support of Raspberry Pi 4 is being constantly improved, the use of Raspberry Pi specfic kernel is not required. Therefore, we can try install Void using EFI boot and generic mainline kernel.