I've used the Dvorak keyboard layout for around a decade now, and I grew up on Mac OS so I am forever familiar with the Option key behavior for typing certain special characters.
Linux (at least KDE) comes with a standard Dvorak layout, and a "Mac" layout that makes the AltGr key behave like the Mac Option key.
However, there is no combined Dvorak+Mac layout.
I combined these layouts by updating /usr/share/X11/xkb/symbols/us to include a new layout called dvorak-mop (mop = mac+option).
I then edited a handful of xml and lst files in /usr/share/X11/xkb/rules so X/KDE can recognize the new layout as well. Also had to delete some compiled keyboard layouts in /var/lib/xkb/*.xkm.
Some or all of these files may be located elsewhere in other Linux distros. Extract the zip file and then either run the install script as super user or manually add the files. If something breaks, restore will hopefully put the original files back. Only tested on KDE with Linux Mint, Kubuntu, and OpenSUSE.
In KDE, you should be able to add the keyboard layout in System Settings => Input Devices => Layouts under Configure Layouts. It will be listed as the English (Dvorak Mop) variant.
If you prefer to just use the command line and have a more minimalist system, you can run setxkbmap -layout us -variant dvorak-mop. Note that if you have a desktop environment, like KDE, running this command directly can cause conflicts.