Guys I am having same problem all the time year after year after year.
When new GPU is out and I am trying to install Ubuntu on new PC I never can't get it to boot in to GUI. It's always same thing, black screen with Nouveau error. If I am not mistaken Nouveau is some sort of driver that is in use during post and if new GPU is not yet supported by this Nouveau I am screwed.
Now I do know there is few ways to install Ubuntu. I remember old msdos looking shell and I really have no problem with it as long as I can get Ubuntu installed and then update GPU drivers with latest available and boot to proper GUI.
Is there a tutorial for this problem I can find somewhere? I am sure I am not only person with Nvidia 2000 series GPU trying to install Ubuntu. Thank you so much guys !!