networking in bpi-m5 with new 26.03.1 release.

[eselarm]

/dev/mmcblk0p1 is a partition that contains the filesystem, not a drive. The drive is /dev/mmcblk0 and because you did a low-level sector by sector (or block by block) copy with dd, it also just has the exact same partition table (MBR-table or GPT). 

Now in modern Linux and various pre-installed images there are methods (possible) to expand the partition and the filesystem to occupy the whole remaining space. It is easier with MBR-table. If GPT, there is a backup GPT at the end of the disk, so in your case 64G. On the 128G SD-card the space after 64G is then hidden.

I usually manage all this manually before first boot, with gdisk, not fdisk. As it is text based, it also works via remote ssh and serial console cable. I also deliberately added a dummy partition (number 3) to RPi images in the past so that the auto-expander could not claim the whole SD-card. If no GUI, a Linux install fits within a few GB, especially if you use Btrfs as filesystem for root and use on-the-fly compression (mount option compress-force=zstd). Then it is about 1GB needed, not 100x more.

Edited 1 hour ago by eselarm