Hey there from Germany,
I unsuccessfully tried to integrate a wittypi2 into Volumio OS. I followed the workaround from uugear for WittyPi2. The download worked well but the install sh was denied. I´m a noob and not familiar with raspbian yet, so i think it´s a small thing to make this work but i can´t solve it myself. Volumio is now running with a raspberry Pi 3B+,a Rasptouch and a 7" Display very well.
I think you need to give us some detail here. A link to your “workaround”, how is it “denied” (give error message? The more detail that you can give, then the easier it is to help 
Problem solved! It was very simple, as there was no unzip installed in Volumio OS. After this was done, everything worked well!