Horray, there is an actual workaround.
Apparently, Corsair cannot handle Unicode very well and resorts to hardcoding en-us.
Luckily, reddit is more helpful than this forum when it comes to such problems:
Requiring users to change their administrative system language to en-us solely due to a company's inability to handle Unicode effectively within their installer is a fundamentally unjust and user-unfriendly practice. Such an approach undermines the principles of inclusivity and diversity that technology should uphold. Unicode is a universal character encoding standard designed to support various languages and scripts, and any modern software should be able to handle it proficiently.
Cryptic error messages exacerbate the frustration experienced by users facing this issue. Instead of conveying helpful information, these messages often alienate users further. Embracing Windows-specific Unicode APIs like wchar_t and MultiByteToWideChar is crucial for software developers to ensure seamless language handling, irrespective of the user's system language.
Companies have a responsibility to develop software that is user-centric and globally accommodating. Forcing users to make substantial changes to their system settings as a workaround for a company's programming shortcomings is an unacceptable disregard for user experience. In an interconnected world, it is paramount for companies to prioritize robust Unicode support and provide meaningful error messages to empower users and foster positive interactions with their software.