I was aware that the ICE40 devices have some limitations compared to other devices that are not so cost and power constrained. Until now the apparent lack of LUT RAM escaped me. I guess it is one of those features that is so ingrained in my mind that I never noticed they don't talk about it. The LP family has a very low end member with only 384 LUTs and *no* block RAM, so I was considering what I might do with the LUT RAM. Not much. They don't mention the LUT RAM anywhere and barely mention the LUTs as ROM only peripherally, but I'm pretty sure that is available since it is the same as logic.
Wow, the 384 LUT part has no RAM at all, so it ends up being incredibly limited.