Wine

Adobe Digital Editions 2.0

1. Install wine and winetricks (apt install wine winetricks/pacman -S wine winetricks)
2. Download installer for ADE 2.0: wget https://download.adobe.com/pub/adobe/digitaleditions/ADE_2.0_Installer.exe
3. (optional) choose wineprefix: export WINEPREFIX=.wine_ade
4. winetricks -q corefonts windowscodecs dotnet35sp1
5. run the installer: wine ADE_2.0_Installer.exe

Calibre + DeDRM + Linux

These modified instructions have been taken from github I installed pycryptodome since it has a nearly identical api and does not need compiling.

1. Follow instructions for Adobe Digital Editions 2.0
2. winetricks -q python27
3. cd .wine/drive_c/Python27 && wine python.exe -m pip install pycryptodome
4. Install calibre (apt install calibre/pacman -S calibre)
5. Install the DeDRM plugin
6. Download the plugin DeDRM_tools Releases on github
7. extract DeDRM_plugin.zip and install it in the calibre gui
8. quit calibre
9. Now when importing a book the DRM protection should automatically be removed (you can check this by running calibre from the terminal and observing the output)

Notes: On Kobo devices some books still show up as DRM protected, even though they are not, I guess that there are some left-over files, configs, whatever. You can simply convert the book to an epub (epub -> epub) and sync the new file, problem solved.