Вячеслав Булынкин

vsftpd

apt install vsftpd -y
useradd ftpuser
passwd ftpuser
echo "ftpuser" | tee -a /etc/vsftpd.userlist

It is not advisable to use FTP without TLS/SSL/FTPS over the internet because the FTP protocol does not encrypt passwords. If you do need to transfer files over FTP, consider the use of virtual users (same system users but with non system passwords) or TLS/SSL/FTPS.

/etc/vsftpd.conf

userlist_enable=YES
userlist_file=/etc/vsftpd.userlist
userlist_deny=NO

https://security.appspot.com/vsftpd/vsftpd_conf.html
https://www.digitalocean.com/community/tutorials/how-to-set-up-vsftpd-for-a-user-s-directory-on-ubuntu-16-04
https://ubuntuforums.org/showthread.php?t=518293