Soldered RAM with a hidden SO-DIMM slot is still a thing.

Yes, but it’s becoming rarer, and “hidden” usually just means you have to get past a metal shield or a rubber cover under the bottom panel.

Think of it as a compromise: one stick of RAM soldered to the board, one accessible slot for later upgrades. This is common in business laptops where the manufacturer wants lower power consumption (soldered) but still gives you an upgrade path for the second channel. Examples from the last few years include some Lenovo ThinkPad T14/T16 AMD models (not all generations, check the model), certain Dell Latitude 5000/7000 series, and a few HP EliteBooks. Gaming laptops do this too sometimes, but they usually just have two SO-DIMM slots without soldering.

The tricky part: manufacturers don’t advertise this well, and they change configurations per region and generation. So if you’re shopping, look for