Kernel panic - unable to mount root fs after upgrade to 20.04

I had this on every or nearly every update from Ubuntu 19.10 to 20.04. No crazy old devices or anything, just plain VMs or bare metal with standard hardware. So I'm wondering why they obviously didn't even test the happy path of a normal upgrade from 19.10 to 20.04, as it HAS to work on a fresh release, no excuses. "Wait for the first point release" is an advice for the LTS to LTS upgrade.

However, leasts-pain-solution for the people without USB-Sticks at hand is:

• Hold SHIFT during boot to get GRUB menu (it will appear after the first failed boot automatically, though)
• Choose "Advanced options for Ubuntu"
• Choose the older kernel in recovery mode (Linux 5.3.0-51-generic (recovery mode))
• In the Recovery Menu, choose "dpkg - Repair broken packages"
• After repair, reboot. Hold SHIFT again
• Now choose "Advanced options for Ubuntu"/older Kernel again, this time WITHOUT recovery mode
• System should now properly boot with GUI. uname -a will show the old kernel 5.3.0
• Simply reboot again
• System should now magically boot with GUI and the new 5.4.0 Kernel