Apple
With the upcoming release of iOS 27 and macOS 27 Golden Gate, Apple is adding a useful feature to its iCloud Shared Albums. It will now let Android and Windows users add photos to these albums, bringing it in line with what you can do on other photo-sharing services like Google Photos.
While Android users previously lacked access to shared albums, Windows users had limited support via the iCloud app. Enabling iCloud Photos on Windows unlocks the option to view shared albums you've joined. On Android, your best bet is using a shared web link, which lets you view the album contents in any browser.