It's still a long way out, but a new roadmap surfaced on the web, mentioning the Ryzen 6000 Notebook series with some broad specifications and features.... AMD Ryzen 6000 Notebook Roadmap Surfaces
Not sure about the Rembrandt-H, but I have a slight impression that Rembrandt-U is going to be a paper launch and won't start being available until 2023 or so (following what's happening with Cezanne-U which is nowhere to be seen half a year after its release date).
