Ubuntu 20.04 not booting correctly

Question

I have a Dell Inspiron 15 5000 with NVIDIA GeForce MX230.
I upgraded my Ubuntu from 18.04 to 20.04 by means of the graphical updater built-in in the system. During the installation of the packages, the system froze and after many hours of indecision I forced a reboot.
I think the system freeze was somehow related to NVIDIA GPU.
Since then I have faced (and solved) many problems related to this broken system upgrade, however I still have a worrying problem related to the system boot.

Basically, this problem can be faced in two different ways:

• Sometimes the initial Dell splash screen freezes without showing the grub2 choices menu.
• Otherwise, when I choose the Ubuntu system, I get the error:

error: Command failed. 
... 
error: Command failed. 
error: you need to load the kernel first.

Press any key to continue...

A trick I use to boot the system is just by restarting it many times until it boots correctly.

To address these booting problems I tried the following:

• Disable secure boot (still disabled)
• Avoid GPU at boot with nomodeset param: https://itsfoss.com/fix-ubuntu-freezing/
• Switch to proprietary NVIDIA drivers: nvidia-driver-460 (proprietary, tested)
• Reinstall grub2 and repair boot with Boot-repair: https://help.ubuntu.com/community/Boot-Repair
• Remove outdated snaps: https://superuser.com/questions/1310825/how-to-remove-old-version-of-installed-snaps
• Remove old kernel images: How to easily remove old kernels in Ubuntu 20.04 LTS?.
  The output of the following command is:

$ dpkg --list | egrep -i --color 'linux-image|linux-headers|linux-modules' | awk '{ print $2 }'
linux-headers-5.4.0-65
linux-headers-5.4.0-65-generic
linux-image-5.4.0-65-generic
linux-modules-5.4.0-65-generic
linux-modules-extra-5.4.0-65-generic

I thought that something is wrong with partitions at boot, but I was not able to discover more.
The most important partitions of my system are:

$ df -h
Filesystem       Size  Used Avail Use% Mounted on
udev             7,7G     0  7,7G   0% /dev
/dev/nvme0n1p8    37G   26G  9,4G  73% /
/dev/nvme0n1p1   746M   91M  656M  13% /boot/efi
/dev/nvme0n1p10  148G  131G  9,0G  94% /home

Why do you think I am getting this boot errors? Should I reinstall my system? In this case, how can I do it safely?

Answer 1

I think a system reinstall is the best way to go, and instead of upgrading (which sometimes work, but some times not) doing a clean install. I had issues with upgrading between "newest" versions of ubuntu, and my system was also freezing and unresponsive. After a clean install, it worked fine again.

How to do it safe depends on your pc. I would customize the partitions, remove everything, and make 1 partition mounted at /. The grub install location should then be set to your ssd, and after installation, you can try reinstalling your graphics driver. If it doesn't work, try again without the graphics driver.