When using any dark Firefox theme on ChromeOS, the contextual menu text and background are both dark. This means there is little to no contrast, and so the text is very difficult to read. Unfortunately, the ChromeOS screenshot tool doesn't work on Linux apps, and so I'm unable to share a screenshot. Tested using several dark themes, including the default -- behaviour was consistent in all. Firefox installed using [https://support.mozilla.org/en-US/kb/run-firefox-chromeos the official package] through the built-in ChromeOS Linux VM "crostini". Issue has been reported by other users on other platforms in the past, so this seems to be a long-standing bug.