Well yes, Fairphone is the only successful example I know, for several failures (Ubuntu, Jolla...). I guess that fairphone offered a product that could find a broad audience, bring ethics in the smartphone world. Good shot
But for volla, what do they promise? Another piece of hardware. Okay, we have already too many of them and it becomes difficult to make a choice. A new android-based ROM focused on privacy. Well, the design looks okay, but nobody cares about this. There are already so many ways to tweak android... Ordinary people don't care about privacy and think that when they have an iPhone they're as far as they can on that point. People who really care about privacy already have solutions (Lineage with microg, /e/), some of them easily available for non-techs (/e/ pre-loaded on a Samsung).
There is the promise that they will support UT, and only for that I could consider investing on the product, because the hardware looks far better than pinephone. But if it is simply a clone of a gigaset model, as some have said here, we could hope to have the port available even if Volla fails...