Thank you for the report. 
Two remarks:
- These lines would not be necessary IMHO:
The options above are meant for an SPI display while you have a DPI display.
- You might try moving the lines you added to “/boot/config.txt” to “/boot/userconfig.txt” and check if they still work. Using “userconfig.txt” has the advantage that it survives Volumio updates.
@moderators Since this thread is about SPI type displays maybe move gattoner’s and my post to a new thread with the title “Volumio with Waveshare 3.5inch DPI LCD”.