Thanks for filing the bug report! I’ve actually just implemented a fix for this issue based on a crash report. This appears to be caused by the integer number format for the configured region locale. Unfortunately I haven’t been able to reproduce the issue on my Linux Mint installation, so there is currently no 100% certainty that the fix actually works. In any case, the fix will be in the next release candidate.
Having said that, you might be able to work around the issue by choosing a different region under “System Settings” → “Languages” → “Region” (might require logging out and in again after the change).
This is hopefully a known Linux issue, where dialogs sometimes appear as black. This is one of the last open known issues scheduled to be fixed for the final release version, although it has proven to be difficult to track down, which is also the reason why it is still in the RC. In fact, at least two attempts to fix this have been implemented over time, but it still happens on some systems, sometimes rarely, sometimes often, without any sign in the logs.
The good news are that I can reproduce it on my laptop and that you can get around it in the settings dialog by pressing tab and then the down key to get most of the window to redraw.
In any case, the next release will either have a proper fix or at least a band aid fix for this.