Are there missing options in default.yml? Or how do I make changes without modifying the code?

[curiosport]

I'd like my instance to have a different language by default. Currently, I can only change the interface language in the account settings, but my goal is for all new users to have a single language by default, one other than English, avoiding the manual work for the user of setting it to their native language.

On the other hand, I don't know if it was in Misskey or if I'm confusing things, but how do I remove the Github icon from the home screen? I remember there was an option to disable that, but I don't remember if it was Misskey.

I currently use this command to start the server:
NODE_ENV=production pnpm run start
I guess that there you can configure what I said before, and if not, I guess my only option is to edit the code but oh wait, I do not want to modify the code because I do not want to complicate the project having to comply with the requirement of the license to notify the modifications because they are not even complex modifications, important yes, but not complex, it makes me ugly to share the source code for changes of such a small scale.

[AmaseCocoa]

I don't think GitHub Corners (like the one in the image) can be removed. in short, you should be edit Misskey's source code (and you must publish source code to platforms like GitHub or following this guide configure to publish source code in misskey interface) if you want remove github corners.

I don't think you could change the default language of the instance (don't take this too seriously, as I may have missed it) but Misskey should detect the client-side language and apply it automatically.