If you use Dvorak for your English layout, it makes sense to also use Dvorak for Bulgarian. I couldn't find one for Linux so I created my own.
Markup : 
Installation is simple:
-
Enable language support in the settings
-
Run the installer
sudo ./install.sh
There are only 3 files that are modified, and all are backed up.
- /usr/share/X11/xkb/symbols/bg
- /usr/share/X11/xkb/rules/evdev.lst
- /usr/share/X11/xkb/rules/evdev.xml
This has only been tested on Ubuntu, it's likely it will work on other Linux distros. If you are on a non-Debian distro, check if the files listed above exist. You'll probably need to restart after the install script is ran.
- Go to Settings -> Keyboards and install the new layout
If you want to create your own version (perhaps for a different language) follow these steps:
- Copy an existing layout from /usr/share/X11/xkb/symbols/
- Modify this layout as you see fit
- Make sure it has unique name
- Modify the install script
- Change the country code
- Change any mentions of "Bulgarian"
Just fork the project, make the changes, then submit a pull request!