Linguaphone did not die in the 80s. They have a modern platform called Linguaphone Connect. It includes the Advanced English level. It is not free, but it costs less than a single textbook per month. Search for this on Google instead of the PDF.
While beginner courses teach how to say simple things, the Advanced course teaches why language functions as it does. It covers: Linguaphone Advanced English Course Pdf - Google
A Structural and Methodological Analysis Linguaphone did not die in the 80s