in case anyone is interested: i have created a newer version of my debian sid image at Release 240519-01 - experimental debian sid image for the starfive visionfive2 riscv64 sbc · hexdump0815/imagebuilder · GitHub - not much really changed (i even used the old kernel build from the last image) aside from that debian is supporting riscv64 meanwhile regularly in its rolling sid release, so there are no more special hacks and repositories required for it
as a nice side effect the image is built from newer and more packages (there is now a firefox in debian riscv64 etc.). the idea of this image is to have a mostly clean debian sid image, which can easily be updated via the normal apt commands etc. - the price for that is that all the fancy (and still often quite broken) parts like gpu support, booting from nvme etc. are simply left out: it is intended to run from an sd card and it uses the framebuffer for xorg without any gpu acceleration … as such it might be a good starting point for own experiments and moving on from there, building own kernels or software on it etc. …
in case you have other riscv64 devices around as well: if you look next to that image you’ll also find a similar image for the bananpi f3 and two basic alpine images for the milk-v duo 64mb and the sipeed m1s dock (which should work on the pine64 ox64 as well if the proper entry is choosen on boot) in other releases of that repo.
good luck and best wishes - hexdump