Doesn't Sailfish have its own proprietary Android compatibility layer, at least in the official/commercial version? Of course that doesn't preclude anbox, but it's another option.
It does, in the Sailfish X variant (the one you pay for). I haven't tried that one, but I have a genuine Jolla phone with a much older version of Sailfish, and I run a lot of Android apps there - they all work fine. What doesn't work for me are apps needing the Google thingy API, which aren't that many.