Hi, I just installed Kubuntu 18.04 on my laptop, and I was wondering if it's possible to have multiple X sessions at once.

For example, I can open as many TTY as I want (only from F2 to F6, actually, F1 seems to be default X session) but, when I type 'startx' or 'startx -- :1' on one of those terminals, the session seems to open fine, but the first one gets corrupted, session is closed and error messages appears all over the screen.

Is there a safe way of doing this? Or is it just a bad idea?

In the case there IS a safe way, since I also installed the 'ubuntu-desktop' package, can I choose to open a KDE or GNOME session via command?

Thanks in advance!

This is totally possible already. There should be an entry in the Leave menu for Switch User which can be used to switch to other X sessions or start a new one. You can also do this from the Lock screen by using the Switch User icon/button.

Once you select to open a new session, it brings up the display manager's login screen where you can pick which session you want to log into.

Now, corrupting existing sessions is definitely weird. I've used this feature quite a bit at home both for having separate logins for different family members as well as occasionally logging into multiple different desktops with the same user simultaneously to try stuff out (usually Plasma+something light like OpenBox; but I don't recall having had trouble with multiple Plasma sessions for the same user, and certainly no trouble with multiple different users logged into Plasma simultaneously).

Sorry for the looooooooooooong delay, but I finally tested it without any problems. My doubt was I the system is able to have multiple X sessions with the same user, but all my doubts are resolved now and things are working perfectly.

Thanks to all for the support.