[DESKTOP] Kubuntu hangs at booting

[Lumaja]

Kubuntu 20.04.2.0
After having problems with booting from USB I eventually sussed and install it.
Booting Kubuntu only shows a black screen and the HDD led on all the time.
I try the way that I got USB going which was pressing Shift while booting the Grub
screen comes with only Recovery or Generic start, click Recovery goes through the process
and then black screen and HDD led on and nothing else.
Can some please help to correct this
Thank you

[bradleypariah]

I came here to report the exact same issue. Commenting to subscribe to this thread. I tried both Kubuntu 20.04 and 21.04, but neither will successfully boot after installation.

My GPU is a gtx680, which doesn't have the UEFI patch (yet), so my motherboard's BIOS is set to EFI + Legacy.

I tried to install Kubuntu by booting into the legacy USB installer, and by booting into the EFI USB installer (they show up as different bootable options in BIOS).
I tried installing the OS with an EFI partition, and without.
I reinstalled Kubuntu from scratch four times yesterday, each time trying to tinker with the settings. Nothing worked.
I've been burning the ISO with Balena Etcher, if that matters.

Oddly enough, I downloaded Ubuntu 20.04.2, and it fired right up.
Partition scheme:
901 MB EFI
460 GB / (ext4)
16 GB /swap

Back story:
The reason I was reinstalling my OS was twofold.
About 20% of the time, my system (Kubuntu 20.04) would boot to a blinking cursor, and I'd have to reboot (possibly two or more times) to get to the login screen.
Also, Composition Pipeline (Nvidia Settings' jargon for Vsync) stopped working correctly, and I killed the Plasma desktop by using the Driver Manager to switch to an older driver.

My hardware is in my signature, but I'm running Ubuntu for the next couple days. I don't like Gnome much, so if I can't figure out what's up with Kubuntu, I was thinking I should try Neon, since it's based on Ubuntu 20.04, which boots just fine.
-or maybe I should just download "kubuntu-dekstop" from synaptic, reboot into Plasma, then uninstall the ubuntu-desktop stuff?

[bradleypariah]

I opted to try Neon 5.21, and it boots just fine.
It sits on the BIOS/boot page for a couple seconds longer than Kubuntu or Ubuntu did, but after multiple reboots, it just works.

What could be so different that both Ubuntu 20.04 and Neon 5.21 would boot with my hardware, but Kubuntu 20.04 will only successfully get to the login screen 80% of the time, and Kubuntu 20.10 won't boot at all?

This whole problem started when my Intel machine died, and I decided to buy an AMD motherboard and CPU. Should I have stuck with Intel??

I do so much customization to my Plasma desktop, that I really hate reinstalling my OS, but I'm kinda antsy to get back on Kubuntu before I get too settled in to Neon.
Don't get me wrong, it's great because it's Plasma, but it's just not the same.
Nowhere near the same amount of community-made themes available through Settings. Steam will only run via Flatpak. There's no driver manager, which is a pain for Nvidia users like me.