Plasma Mobile supports the Nexus 5 and (maybe) the OnePlus One right now. CopperheadOS doesn't support either of those. I was unable to get a reliable source for supported devices for Ubuntu Phone (best I found was [1], not even sure if that's related) and so far I don't believe that the supported devices for THAT platform intersect with the other two.
Searching for sailfishOS device support only comes up with Jolla phones. It seems as if not only is the market lacking alternative systems, it's also near impossible to try out the ones that do exist. Buying a device for some experimental OS is something I have done (Flame for FxOs - still sad that it died, owned a Palm Pre), but cumbersome and expensive.