On a DDR4 motherboard the training would occur between the memory controller and the DDR4 RAM. The proprietary blob you need would include the communication with the memory controller and instructions to handle the training for that specific memory controller.

There are several open source DDR4 controllers in different states of usability. They have each had to develop their own implementations.

Note, it is actually easier to profile a known dram chip set bonded to the PCB. A lot of products already do this like phones, tablets, and thin laptops.

Where as SSD drives being a wear item, should be removable by end users. =3

Surely someone can do it, but it's probably too niche to do. The licensing fee is probably cheaper than corporation spinning the board and reverse engineer it and for hobbyists lower tier memory likely was fine.

That said given that such technology has become so much more accessible (you can certainly create FPGA board and wire it up to DDR4 using free tools and then get board made in China), it's probably a matter of time someone will figure this out.