Good news! I've figured out the issue! Bad news, idk if we'll need to wait until the next update. Let's try this quick method first to gauge how borked it is:
Change the folder's name to be all lowercase. If we get a new error then it's just a capitalization bug, which I cannot fix on the engine's side, but I can update my character folders to ease the pain of needing to perform [rename -n 'y/A-Z/a-z/' *] in each directory level for each character.
Basically in GMS2, to prevent crashes and errors in Linux environments, it automatically lowercases text given to file reading/writing functions. The "characters" folder in the screenshot exhibits this behavior since on Windows platforms the folder would be "Characters" with a capital C. That screenshot is doing some heavy lifting lol 😂
To explain the bug further, I grab all the character folders in the main "characters" folder, which would probably grab their name as is (with capitalization). But when it goes to read it, it'll automatically get lowercased and so a mismatch happens. It acknowledges that the folder exists with ".../FolderName/..." but it can't access it because it's looking for ".../foldername/..." instead. Hence why it says the Struct.ini file is missing since I accounted for it not finding the file in the folder, not that you can't find the folder when it was already found 😆
Let me know if that method progresses the error, and if it does then just lowercase all the files to fix it. If it doesn't, then it will be in next update to address this. Either way, hope you have a good day! :3