I am using a micro SD Card and an adapter on Gentoo Linux. The SD Card device name is mmcblk0
with 2 partitions. mmcblk0p1 being the boot partition and mmcblk0p2 being the root partition.
anthony@anthony ~ $ sudo dd if=/home/anthony/Documents/IMGs/rpi4b_system_image.img of=/dev/mmcblk0 status=progress bs=512
3218899456 bytes (3.2 GB, 3.0 GiB) copied, 564 s, 5.7 MB/s
6291456+0 records in
6291456+0 records out
3221225472 bytes (3.2 GB, 3.0 GiB) copied, 573.351 s, 5.6 MB/s
anthony@anthony ~ $