I followed up the procedure below
to create FTP on Ubuntu 20.04 server but after that I cannot put files into FTP (got issue of no proper permission below).
Within Ubuntu server, I do verify all is fine to FTP like
root@jamesubuntu20:/etc# ftp 192???
Connected to 192???.
220 (vsFTPd 3.0.3)
Name (192???:james): ftpuser
331 Please specify the password.
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.