Yes, Sigil will run fine in Xubuntu. At one time I created a virtual Xubuntu machine expressly for running Sigil. I chose Xubuntu because of the relatively light-weight desktop environment (that is, light use of resources).
It will take some adjustment on your part to get used to the slightly different way of doing things on the XFCE desktop vs. the windows desktop, but the basic principles are the same. Kind of like driving a different make of car -- the controls may not all be in the same places, but they are still there.
Anyway, learning new things keeps Alzheimer's at bay!
Albert