Function install_via_bootupd 

pub(crate) fn install_via_bootupd(
    device: &Device,
    rootfs: &Utf8Path,
    configopts: &InstallConfigOpts,
    deployment_path: Option<&str>,
) -> Result<()>

Install the bootloader via bootupd.

When the target bootupd supports --filesystem we pass it pointing at a block-backed mount so that bootupd can resolve the backing device(s) itself via lsblk. In the bwrap path we bind-mount the physical root at /sysroot to give lsblk a real block-backed path.

For older bootupd versions that lack --filesystem we fall back to the legacy --device <device_path> <rootfs> invocation.