Question: I'm a very long time ubuntu user (over a decade) but have not been here as I've had no issues with Ubuntu. With the arrival of 20.04 LTS I decided to encrypt my data (or system if needed). I'm looking for the following:

* Method to reinstall ubuntu with LUKS encryption on a previous LUKS encrypted ubuntu install on a dual boot system with Win10.
* Keep all my personal files (ie `/home` folder) intact, with or without a separate partition. I do not wish to move everything out, reinstall and then move stuff back in.
* Simple GUI based approach through the standard installer. I know how to use the command line but I'd rather not, especially for something as sensitive as encryption.

What I'm looking for is basically the same as this document: (<https://help.ubuntu.com/community/UbuntuReinstallation>) except that I need it on an LUKS encrypted system/partition. I tried doing this on a spare system with 20.04, and I could not find a way of telling the installer the passphrase to the encrypted system. The end result was a reinstall that wouldn't boot or the encrypted partition gets wiped out. I also tried to run installer with and without pre-unlocking the encrypted partition but to no avail'.

I am able to do all of the above with Fedora,OpenSUSE,Manjaro, (although they only do this when /home is on separate partition, which is fine for me) so I'm not sure what I'm doing wrong in Ubuntu.

Thanks!

Answer: 
For video playback in the browser you only need to install the package `ubuntu-restricted-extras`. To do so open a terminal and type:

```
sudo apt install ubuntu-restricted-extras

```

Should that still fail with the error message you posted above, reboot and try again. Should the error persist, a previous update might have been interrupted and left the lock file in place, as Pilot6 commented above. To fix that:

1. In a fresh terminal type `sudo rm /var/lib/dpkg/lock-frontend`
2. Then make sure, all packages are installed correctly with `sudo apt-get -f install`
3. Make sure the codecs are installed correctly with `sudo apt install ubuntu-restricted-extras`. When you are prompted to accept the EULA for the Microsoft fonts package, use `Tab` and `Enter` to agree.

After restarting your browser, video playback should work.
I tried and failed to get videos to work.
I install both clv and mpv and found that both worked.
I chose to set music and video in Settings -> Default Applications to mpv.
Whist I was fighting videos I may have install various codex which might just be essential to mpv.