Hi!
I upgraded from 18.04-2 to 19.04.
Before I used kernel 4.15.0-54-generic and with this I had no problem on boot but
after upgraded to 19.04 I can't boot with kernel 5.0.0-20-generic.
It hangs and boot stopped before enter password for encrypted partition on boot.
I switched back then to kernel 4.15.0-54-generic and with this 19.04 booted.
Does anyone have any idea why?
I am on LTS, so I can't say this for sure--- but the normal supported upgrade paths are from one LTS to the next (16.04 to 18.04 to 20.04). Or from one regular release to the next.
18.04.2 (which is LTS) directly to 19.04 skips 18.10. Maybe all the dependencies and updates are handled correctly, and maybe not.
Again, I'm not sure this is your problem, but it is my first thought.
Before upgrade from 18.04-2 (LTS) to 19.04 I switched in "/etc/update-manager" to "Prompt=normal" and then upgraded to 19.04.
It's strange that the kernel 5.0.0-20-generic don't run on my system.
I'll keep trying around to get it to run and let you know here when it runs with a higher kernel.
I found the solution for my problem with the new kernel 5.0.0-21-generic.
It was the vfio driver.
I blacklisted vfio module and now I can start with kernel 5. 0. 0-21.
But I have a new error with i2c driver on boot. (I don't have i2c packages installed)
Systemd shows me i2c errors:
kernel: [ 14.509890] i2c i2c-2: SMBus Timeout!
kernel: [ 14.509952] i2c i2c-2: Failed reset at end of transaction (01)
kernel: [ 14.510064] i2c i2c-2: Failed! (01)
How can I fix that?
Can I blacklist i2c module?
Also, nvidia396 problems with the new kernel 
Got it, nvidia-driver now working...
removed nvida396 driver and all packages from nvidia396 and installed nvidia430.
In mate-terminal:
ubuntu-drivers devices
I choosed the 'recommended' nvidia-driver.
sudo apt install nvidia-driver-430
I started a new thread of the i2c errors:
What you did in update-manager is irrelevant. That only determines when you are prompted to make updates, and whether you are on the LTS or normal path.
18.04 to 19.04 is NOT a supported upgrade until after end of life for 18.10. Sometimes the upgrade manager must run scripts to change config file formats or other organizational things that are not covered by the package dependency system. This is made abundantly clear in the Ubuntu wiki and manuals.
It is entirely possible that 18.04 to 19.04 would work for some people and hardware and not for others.
Maybe it is your problem and maybe not. Supposedly, after EOL on 18.10 you can go straight to 19.04, but there is no easy way to tell if the scripts for update-manager have been changed yet. They are not due to change until end July.
Why don't you try 19.04 on a liveUSB and see if you have the same problem. If that works normally, I would suspect that you have bollixed (a technical term 
your install with the unsupported upgrade and should reinstall 19.04 from scratch. You need not lose anything in /home partition to do this
I'm now on 19.04 with,nvidia430 and kernel "5.0.0-21-generic".
(SOLVED)