Earlier quoted context omitted.
So I have an update! I bought the HiBY R2 II directly from their website it shipped immediately (on a weekend!) and I had it in my hands (in Ireland) less than a week later. It's basically everything the Shanling Q1 should have been. It's slimmer, almost half the weight, has a sane OS (so there's no need for Rockbox) and sounds great. Also had better battery life than the Q1 and you can play/pause using an inline rem…
My own update: decided to dust off my old iPod and repair the fault LCD, battery and hard drive. The (minor) downsides: modern features like Bluetooth and USB-C are possible, but only through soldering. Rockbox unfortunately lacks polish, and it for some reason turns itself off after a while playing music.
In fact I might buy two, because I know they'll discontinue this thing and I don't know if anybody will make anything like it again.