… it imported all the topic threads from the old defunct forum.
The main problem with posting here is that Ruby threads do no work well inside the embedded Ruby that SketchUp uses. So there may not be many who could answer your questions here.
When you post in a Windows-only software forum about running on Linux, the general assumption is that you run the software through Wine. Are you running the Ruby code using the Windows Ruby interpreter through Wine, or using the Linux Ruby interpreter?
Threading on Windows works very differently from Unix-like systems (where Ruby originates from). There have been reoccuring threading problems with Ruby when you emulate Windows threads with Unix threads. If you are using Wine, I’d test on the latest development version (e.g. 5.21) and then go to the Wine forum or mailing list and post the Wine debug/error (not only the Ruby exception above).
If it is natively on Linux, then – as others said – the SketchUp forum is not an appropriate place, rather stackoverflow or the official Ruby mailing list or IBM support. After all it’s their problem and one of their most widely used platforms.
Maybe you could reformulate your problem to get more attention and to make it easier to help. The error is not “report_on_exception is true” (that just means that the child thread should not just silently die but raise the same exception in the main thread). The title should rather be something like “IBM_DB.server_info causes SystemStackError”.