Perfect Debian Buster inside of lxc container fail on FTP autenticathion

Hi!
I am a happy server administrator who has historically configured used ISPConfig with no problems.
For 2 years now, I have been implementing different servers through an Ubuntu 18.04 server and multiple containers using LXD / LXC.
So currently I have containers running Ubuntu 16.04, Ubuntu 18.04 and Debian 8 following the instructions "THE PERFECT SERVER".

The problem.
I have been trying to configure a container with Debian 10 with "Apache" for a week and when executing the documentation step by step, the only problem I had was with the MariaDB service, which forced me to configure the execution of the container with the parameter: security.nesting: "true "
Now once the configuration is finished, I can not authenticate an FTP user, both with Filezilla and with other clients, from Windows 10 or Ubuntu 20.04 as a desktop client.

To eliminate doubts, I made the same configuration on a virtualized machine with Virtualbox on my Laptop and the FTP connection worked wonders.
Before writing this comment, perform multiple searches on Google without getting information to guide me with a possible solution.
Just a clarification: on the Virtualbox machine, I had to execute the command "su -" as it appears in the step-by-step instructions. In a container installation, the entire installation is done with the root user and "su -" generates a "mesg: ttyname failed: No such device" error

Any help or guide that allows me to solve this problem I will be very grateful.

Thanks in Advance!
Luis Ludovico