Here, but they are not as good as yet hence the link on that site to the old guides as well https://www.manager.io/guides/
Do not expect anything, except the new guides which I deem inferior, to be up-to-date. There have been discussions on this for example Manager Guides images not displayed so no need to keep this one going. You made the correct observation that many images are not accessible but this was also reported before. Therefore I will close this discussion.