Full-size DIMM adapters for soldered RAM laptops don’t exist.

No. There is no reliable adapter that lets you plug a regular desktop DIMM into a laptop that only has soldered RAM.

The reason is simple: soldered RAM is physically part of the motherboard. There’s no connector to tap into. Even if a laptop has a proprietary slot for an SODIMM (some do alongside soldered RAM), that slot is for laptop-sized memory, not desktop-sized. The electrical layout, signaling, and physical space just don’t line up.

What you’re describing would require a custom PCB that bridges the memory bus directly to the CPU, with BIOS support, thermal clearance, and a chassis that somehow fits a desktop stick. No one makes that, and it wouldn’t be reliable if they did.

If your laptop has soldered RAM and you need more, you’re out of luck. Buy a different laptop next time.