The quick answer is to use the xPack forums; please select the correct forum.
Check the documentation
The xPack GNU RISC-V Embedded GCC provides the original documentation in the installed folders:
Use the SiFive support channels
For issues related to the toolchain functionality (compiler, newlib gdb, etc) please report them via their original RISC-V projects:
Check the FAQ
Check the FAQ for similar problems.
Check the xPack forums
Check the xPack forums for similar problems.
Check the GitHub issues
Check the GitHub issues tracker for similar problems.
Ask questions in the forums
If you still could not find a solution, if you have interesting use cases, if you have custom configurations, and generally if you have any experience that you want to share with others, use the xPack forums, and enter a New Topic in the GNU RISC-V Embedded GCC section.
Register a new support ticket only if necessary
If you are convinced that you identified a bug (if you have doubts, use the forum), or you have a pertinent suggestion how to enhance the xPack GNU RISC-V Embedded GCC distribution, register a New Issue in the the GitHub issues tracker.
Use of private e-mail
Sending private messages will be automatically replied with a link to this page. The reason for this rude behaviour is simply an attempt to use the time more efficiently; since forum posts are archived, other people having similar problems might benefit from the answers.Edit
Comments on the content of this page that might be useful for other readers are welcomed here. For question and general support, please use the project forums.