The Internet Archive is a public repository, meaning anyone can upload files. You must be careful to distinguish official files from modified or malicious ones.
The official Microsoft website often forces you to download the "Media Creation Tool" (an .exe file) rather than a direct ISO. If you are on Linux, macOS, or a work-restricted PC, that tool is useless. Archive.org provides direct HTTP downloads of the raw ISO file.
A search for "Windows 11 ISO" on Archive.org yields a variety of results, generally falling into three categories: