External RAM over USB-C isn't a thing.

No. You cannot add more system RAM to a soldered laptop via USB-C.

The reason is simple: the memory controller is physically wired to the CPU and the motherboard’s memory bus. USB-C is a totally different protocol (USB4/Thunderbolt, not DDR). Even if you plugged in an external RAM module, the computer’s brain has no way to treat it as main memory. It would just see a weird storage device.

What you can do is use a fast SSD over USB-C as swap/virtual memory, but that’s not the same as adding RAM. It’s much slower, wears out the drive, and won’t meaningfully speed up tasks that are bottlenecked by RAM. If you’re maxing out your soldered RAM, the real answer is: buy a laptop with upgradeable RAM next time. This machine is stuck.