I believe there is a rotary encoder plugin for volume control, but it will depend on which HAT / output you use if there is actually volume control available.
In my case I use a digital-only output direct to an external DAC (Schiit Modi3+), which does not give me volume control from Volumio. If you use a DAC HAT (RCA/XLR out), then volume control should be functional and hence the rotary encoder physical volume control might be cool for you.
Slick case though, and I looked at that same LCD…