In OpenStack's disk image-builder we're using boot GUID bc13c2ff-59e6-4262-a352-b275fd6f7172 (see https://uapi-group.org/specifications/specs/boot_loader_specification/#the-partitions) to identify boot partitions - in current CentOS Stream 10 image the root partition is marked as such:

1. blkid | grep nbd
   /dev/nbd0p2: SEC_TYPE="msdos" UUID="5343-F5AC" BLOCK_SIZE="512" TYPE="vfat" PARTLABEL="primary" PARTUUID="1a1ea6e5-20c0-46a1-9b93-74e5a9eddcae"
   /dev/nbd0p3: LABEL="root" UUID="7917f589-659e-49af-ba77-001a240cb02e" BLOCK_SIZE="512" TYPE="xfs" PARTLABEL="primary" PARTUUID="38481421-edb9-4f1a-9d9a-04c41813135f"
   /dev/nbd0p1: PARTLABEL="primary" PARTUUID="d96fa58d-deb3-45c2-850b-cf0cccf7794a"

1. lsblk -p -o NAME,PARTTYPE
   /dev/nbd0
   ├─/dev/nbd0p1                   21686148-6449-6e6f-744e-656564454649
   ├─/dev/nbd0p2                   c12a7328-f81f-11d2-ba4b-00a0c93ec93b
   └─/dev/nbd0p3                   bc13c2ff-59e6-4262-a352-b275fd6f7172