I have some amount of confidence that the sellers on AliExpress will figure out how to create cheap hardware that makes use out of all of this when it hits the secondary market.
For standard desktop CPUs, the memory controller doesn't support the signaling required to communicate with an RDIMM. There's no clever AliExpress adapter that will magically give a component within your CPU capabilities that it simply doesn't have.
However, if you have a true workstation, you don't even need some adapter from AliExpress! Xeon 600, Threadripper 7000, Threadripper 9000 all support RDIMMs natively.
If an AI crash left the market with a glut of RDIMMs, we would absolutely see AliExpress sellers removing the individual DRAM packages from used RDIMMs and installing eight out of ten of them onto empty UDIMMs. The overhead costs would be a quick bit of hot air reflow, a 5V PMIC and associated components, and a new module PCB, and the sellers would get to build 10 UDIMMs for every eight RDIMMs they scavenge.
For standard desktop CPUs, the memory controller doesn't support the signaling required to communicate with an RDIMM. There's no clever AliExpress adapter that will magically give a component within your CPU capabilities that it simply doesn't have.
However, if you have a true workstation, you don't even need some adapter from AliExpress! Xeon 600, Threadripper 7000, Threadripper 9000 all support RDIMMs natively.