Don't know why my av8805 is not automatically showing the availability of new fw. Just in case others have the same issue, you can use this link to marantz jp website to find if there are new firmware and the changes
https://www.marantz.jp/ja-jp/support/FirmwareUpdate/av8805
This should cover for the rest of the marantz models
https://www.marantz.jp/ja-jp/support/firmwareupdate
https://www.marantz.jp/ja-jp/support/FirmwareUpdate/av8805
This should cover for the rest of the marantz models
https://www.marantz.jp/ja-jp/support/firmwareupdate