Hey, sorry for formatting, but I am on my phone. Am setting up kubuntu for a friend and one of the programs he wants installed is asking for the default display manager or which to use. What is the default for kubuntu?
I have the choice for g3dm or something and sddm.
sddm is default for KDE, I guess kubuntu didn’t deviate from that.
You wouldn’t want Gnome dependencies on a KDE system 
Crap. So my friend got sick of waiting and chose g3dm or whatever it was for the app. Did he screw something up?
Did it actually install a second Display Manager? It may or may not work fine. Issues logging in would be the first noticeable thing.
I had an issue following a guide to roll my own LXQt (borrows from KDE) a few years ago. I installed LightDM as per instructions and it worked but login was all sorts of messed up. I later came across something on the Arch Wiki referring to SDDM as the appropriate Display Manager. Nuked, did it right, ran for months without problems. If there are no obvious disasters then it is probably fine. I don’t know if you can just install one and then remove the other without borking something.
The real curiosity is what program asked for this info and why.
It’s mostly Xserver freaking out some dependencies are missing for other display managers. SDDM heavily relies on SPECIFIC Xserver portions, and all the others use different Xserver dependencies. Kubuntu doesn’t fetch everything and there could be PPA differences, so you need to be 100% certain xorg.conf is a good config or your DM will crash upon boot.
So after some digging I got it back on sddm and found a way to get rid of gdm3. He didn’t remember what program was asking for it. But everything is going good so far.
When I got there it was booting into gnome desktop. Don’t know why. He didn’t want it. So got rid of that and got him back where he used to be. If this doesn’t work I’m gonna just have him reinstall, with me in the room and I’m gonna see what program he installed that asked for it.
Did your buddy start with an existing Ubuntu setup, then install KDE on it? That way secretly leads to madness, even if the installer does mostly work, and can replace gdm with sddm from a simple apt command.
I presume he didn’t, but if he did, he might keep hitting snags that would be avoided by a Good backup, then a Nike and pave.
If you start with Kubuntu, you already are at a disadvantage for dependencies. Switching to GNOME on Kubuntu requires many more dependencies that aren’t in the base ISO.
Nope, we started off fresh with Kubuntu.
He can’t remember what program it was. I was off in the little lads room at the time. But everything seems to be working fine now. Thanks for everything guys, will update if it doesn’t work out.