I'd like to have Pantheon as another session option, next to GNOME and Ubuntu's GNOME variant.
Is there a way I could install Pantheon on Ubuntu 19.04 without messing up various parts of my system? (E.g. the theme changing, maximize and close window buttons changing placement, etc.)
(I would like a full-fledged system, not a system running in a VM)
I'm sharing my experience with installing pantheon desktop on top of Ubuntu Budgie 19.04. Ubuntu's main GNOME edition should work similarly.
First, add these two ppas ppa:elementary-os/stable and ppa:elementary-os/os-patches.
When you install the first ppa with this command sudo add-apt-repository ppa:elementary-os/stable, it will create the repository source file in /etc/apt/sources.list.d. Edit that file to change the distro name from disco (19.04) to bionic. Then re-run sudo apt update
After installing both ppas, add Ubuntu 18.04's main repository source line. You can edit /etc/apt/sources.list file or edit one of the elementary's source file in /etc/apt/sources.list.d/ directory. Add this line (or any other bionic mirror of your choice)
# ubuntu bionic repo for some packages
deb http://archive.ubuntu.com/ubuntu bionic main
Then run these
sudo apt update
sudo apt install elementary-desktop
Add elementary's appcenter's source to get some more elementary apps.
In /etc/apt/sources.list.d/appcenter.list, add these
deb http://packages.elementary.io/appcenter bionic main
# deb-src http://packages.elementary.io/appcenter bionic main
Then refresh the package index and open appcenter to find curated elementary apps
