And then there are deployments in QubesOS, Xen, Nitrokey, etc. Bear in mind that MirageOS is a library OS, which doesn't just mean "compile to a standalone kernel instance". It just means that it can be linked into all sorts of embedded environments, some of which are the solo5 or Xen backends you see in talks.
Not asking to be antagonistic, asking because I think unikernels are really nifty, and genuinely curious if they've worked out for anybody.