There is another new Rust/UEFI project:

alloc_uefi: Rust allocator for UEFI environments.
Usage: Add alloc_uefi as a dependency, and provide the following function as your application’s entry point:
pub extern fn efi_main(sys_table: *const internal_uefi::SystemTable, image_handle: *mut internal_uefi::CVoid)

https://github.com/csssuf/alloc_uefi