Like always, it depends. The hardware section on the wiki lists some device specifics¹, and if you follow the OnDebian² links there are a couple that look like they might work-ish out of the box. Presumably -- or perhaps hopefully -- things will improve quicker with mainline Debian as an option and hardware becoming more available.

In the context of Debian, let us hope people aren't flashing a BSP³ in the hope of improved board support ;)

¹ https://wiki.debian.org/RISC-V#Hardware

² https://wiki.debian.org/InstallingDebianOn

³ https://wiki.debian.org/BSP