How to install Deepin desktop in ubuntu 19.04

Question

I tried this command but it doesn't work

sudo add-apt-repository ppa:leaeasy/dde

it says

Reading package lists... Done                                                  
E: The repository 'http://ppa.launchpad.net/leaeasy/dde/ubuntu disco Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

I also tried changing "disco" to "bionic" in /etc/apt/sources.list.d/leaeasy-ubuntu-dde-disco.list

but when I try to install it with this

sudo apt-get update
sudo apt-get install dde

it says

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 dde : Depends: dde-desktop but it is not going to be installed
       Depends: deepin-wm but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

I also tried

sudo aptitude install dde

it installs but I am not able to start dde with startdde because the binary is not in the path.

I also don't see any Deepin entry in login menu.

and I tried all answers in Unable to correct problems, you have held broken packages and What can I do if a repository/PPA does not have a Release file? but no luck.

does anyone know how can I install dde?