The old url at http://mitpress.mit.edu/sicp/full-text/book/book.html is now 404, and most of what you find on that site will try to get you to do an "eTextbook rental".
The last release is from January 2023. Seems fine enough for learning.
https://www.gnu.org/software/mit-scheme/
The old url at http://mitpress.mit.edu/sicp/full-text/book/book.html is now 404, and most of what you find on that site will try to get you to do an "eTextbook rental".