If you wound up here due to having perfectly good JSON but you still get the error above, I have a question for you:

Did you transfer a file from a Windows to a WSL context?

Because if you did, that file is going to be shredded moving from the Windows Ansi /r/n context to the linux Unicode /n standard. If you are using VScode or something, copying the contents of the file over should be enough to get it to convert properly.