All known issues are documented in the DarkRadiant Bugtracker, which is heavily frequented by the developers. It also functions as development ToDo-List.
Feel free to report bugs (site registration required) to assist the development of the editor. Also, consider dropping by in The Dark Mod Forums to discuss a problem with other mappers.
Use OrbWeaver's PPA, or a darkradiant package for Debian, which is usually available after some time in Ubuntu as well.
Download the Flatpak version from Flathub, or search for it in Discover or GNOME Software.
See the Compilation Guide on our Wiki to build DarkRadiant fresh from its sources.