Looking for logging into the Ftp As Www-data site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the Ftp As Www-data site. After that you can login as usual with your login credentials.
https://askubuntu.com/questions/647392/user-access-to-ftp-and-at-same-time-set-www-data-as-owner-group
https://stoertebecks.com/ftp-user-fuer-apache-webserverzugriff-erstellen/
https://www.digitalocean.com/community/questions/should-i-enable-a-password-for-user-www-data
https://debianforum.de/forum/viewtopic.php?t=66798
https://serverfault.com/questions/143552/owner-of-uploads-directory-is-www-data-but-this-prevents-ftp-access-via-php-sc
https://www.whatmarkdid.com/web-servers/setting-apache-permissions-www-data-ftp-user/
https://www.debinux.de/2014/11/website-verwaltung-mit-sftp-statt-ftp/
https://unix.stackexchange.com/questions/304056/ubuntu-server-16-04-get-full-ftp-access-to-var-www
https://ubuntuforums.org/showthread.php?t=2244861
https://www.linuxquestions.org/questions/linux-server-73/www-data-password-authorization-newb-627578/
https://www.cyberciti.biz/faq/ubuntu-add-user-to-group-www-data/
https://www.youtube.com/watch?v=JuYfEq4VIWQ
https://www.atulhost.com/www-data-sftp-user-setup