“Hash sum mismatch” error due to identical SHA1 and MD5 but different SHA256
Try this before running apt:
$ sudo bash
# mkdir /etc/gcrypt
# echo all >> /etc/gcrypt/hwf.deny
Because apt use sha256 method from libgcrypto20, but optimized too much. We can deny this opt. using configuration file /etc/gcrypt/hwf.deny.
Disable Windows Subsystem For Linux and Virtual Machine Platform if you're using Windows and VirtualBox. Happened to me when trying to install lubuntu 20.04 using VirtualBox 6.0.4 and WSL2 was enabled.
EXPLANATION and Solution: Quick Fix
This issue is caused by the Windows Hypervisor Platform. This issue cannot be resolved for now (asfar as I know).
A partial fix is at hand though. And I say"partial" because it involves disabling the platform (also known as"Hyper-V") which will probably break other virtualization solutions you have installed since this is enabled manually. Anyway, here's how to disable it and get your VM running again,
Shut down the Virtual Machine.
Press Windows logo key + X, then hit A to run Command Prompt(powershell) as administrator.
Type bcdedit /set hypervisorlaunchtype off
4.When you see"The operation completed succesfully", reboot your windows. After reboot, boot your VM and update/upgrade.