Virtualbox broken after a dist-upgrade -- cannot install virtuabox-dkms nor run modprobe vboxdrv

Solution 1:

Update

Note:
- This guide will become irrelevant in the near future when proposed migrates to release.

• 6.1.16-dfsg-6~ubuntu1.20.04.1 is now in the Store 'ubuntu-focal-updates-multiverse' and 5.8 kernel had a few updates with current 5.8.0-40-generic
  Should not be an issue if one keeps up with regular updates.

• Suggested options 1 and 4 to have future automatic updates for VirtualBox.
• Option 2, 3a, 3b manual installation does not include automatic future updates for VirtualBox.

Bug

• [SRU] virtualbox 6.1.10-dfsg-1~ubuntu1.20.04.1 ADT test failure with linux-hwe-5.8 5.8.0-25.26~20.04.1
• virtualbox 6.1.16-dfsg-6~ubuntu1.20.04.1 source package in Ubuntu

Installation of VirtualBox 6.1.16 on Ubuntu 20.04

Option 1 (Easy)

Pre-released updates (focal-proposed)

1. • Open Software & Updates
   • Developer Options
   • select ✅ Pre-released updates (focal-proposed)
   • select Close
   • on Popup The information about available software is out-of-date
     select Reload
2. • Open Software Updater
   • deselect all/any other updates except VirtualBox (which will include multiple packages in its subcategory)
   • select Install Now
3. • Repeat step 1 to disable Pre-released updates (focal-proposed) You don't want to update other proposed updates unless you are familiar with what it entails.
     Ref. Testing/EnableProposed - Ubuntu Wiki, ProposedMigration - Ubuntu Wiki

Previous post

Bug virtualbox-dkms 6.1.10-dfsg-1~ubuntu1.20.04.1 fails to build with kernel 5.8
I followed @Terrance advice and installed 6.1.16 from the source.
My previous VMs are all working.

Edit: Per @BeastOfCaerbannog request/suggestion.

Installation of VirtualBox 6.1.16 on Ubuntu 20.04

Option 2 (Easy)

• Go to Download VirtualBox for Linux Hosts
• Under VirtualBox 6.1.16 for Linux
  Click Ubuntu 19.10 / 20.04
• Open with GDebi Package Installer
• Install Package

*if GDebi is not installed > go to Software Store and install it
*if Error: Conflicts with the installed package 'virtualbox-qt' > go to Software Store and Remove Virtualbox 6.1.10

Option 3 a. (Easy)

• Go to Download VirtualBox for Linux Hosts
• Under VirtualBox 6.1.16 for Linux
  Click Ubuntu 19.10 / 20.04
• Save File in Downloads
• Go to Downloads
• Right Click downloaded package > Open With Software install (or double click, or select and enter/return)
• Install

Option 3 b. (Advanced)

• In Terminal

cd Downloads 

sudo apt install ./virtualbox-6.1_6.1.16-140961~Ubuntu~eoan_amd64.deb

or

sudo apt install ./v*  

Option 4 (Advanced)

 
thanks @Terrance

Solution 2:

Choose the latest working 5.4 kernel instead.

I have 20.04 and this worked for me:

sudo grub-reboot "1>4"

sudo reboot

Or just manually choose the 5.4 kernel at boot.

I guess this bug will be fixed for Ubuntus 5.8 kernel soon.