This part of the emmc is meant to be only read and written by trusted software.
As it turns out you can read this partition on some devices. It is possible if you have a "CMD12" emmc. If it is a "CMD13" emmc it doesn't work. Read operations happen from within linux, also information about the emmc is gathered there, use the following commands:
sudo mmc extcsd read /dev/mmcblk1rpmb > extcsd.txtsudo mmc rpmb read-block /dev/mmcblk1rpmb 0 128 rpmb.img
The extcsd.txt file will contain extcsd information of your emmc, the rpmb.img file will contain the RPMB dump, if dumping works.
If you happen to do this process contact @utf-4096 on our discord server, as he is interested in this information (if dumping worked and in the extcsd info).