How to resolve the NOMODESET causing black screen problem for older Nvidia Cards in Kubuntu?
Solution 1:
Your card is somewhat older (it is good to keep the the old hardware alive) but you will have to install an older nvidia driver before you could get rid of the "nomodeset".
Add the "nomodeset" to grub again, install the Nvidia 340.xxx driver - then you should be go and remove that flag again. See installing Nvidia 340 driver which has been asked recently.
Don't forget to update-grubafter the changes you've made in /etc/default/grub