Want access to root directory from remote computer via Dolphin or Gnome Files app

I am setting up a new computer in my home. Both my old computer and my new one run various flavors of Ubuntu Linux, the new one Kubuntu 24.04.1, the old one Ubuntu 24.04.1. There are certain files on the old system that I want to copy to the new one. I have the sshd_config files set to permit access by my username with ChrootDirectory / I find the following situation occurring: running command-line sftp, I can connect to the other computer and successfully do cd /. Also, running FileZilla I can get to the root dir of the remote. However with Dolphin, though I can make an sftp://myname@remote connection, after entering the password, I can't go above /home/myname. Similarly, as an experiment I can make the reverse connection from the old computer to the new one. I also, though, cannot get above my home directory. How can I make this work, and in particular, if FileZilla and command-line sftp manage to do so, why can't Dolphin or Gnome Files do it?