External RAM via USB-C or Thunderbolt doesn't exist.

No. You cannot add system RAM through a USB-C or Thunderbolt port. RAM requires a direct, low-latency connection to the CPU’s memory controller. USB and Thunderbolt, even at their fastest, introduce too much latency and bandwidth overhead.

What you might see marketed as “external RAM” is usually a scam or a misunderstanding. Some products use an external drive or memory card for virtual memory (swap), but that’s not adding RAM—it’s just an external SSD with a fancy name. That’s slower than internal RAM and won’t give you the performance boost you expect.

If your goal is to speed up an older laptop: upgrade the internal RAM if it’s user-serviceable, or consider a new machine. You can’t bypass the physical limits of the memory bus with a cable.

Don’t waste money on a product that promises to add RAM over USB.