Hello!
I created a simple script that allows you to use unity's mecanim for spine animations. The scripts are generalized enough so that you can use any spine animation. The repo contains the latest unity spine runtime and the scripts I made. There is also a readme that hopefully explains the tool well enough.
I've also provided a scene where I created a sample mecanim for spine boy.
While I was able to leverage unity's mecanim to create FSMs for spine animations, more custom aspects of spine's runtime are not implemented (e.g. queuing animations, custom blend times). The tool is for simple spine animations that do not need to use those things.
gitlab repo : https://gitlab.com/raphael.reventar1/unity-spine-extensions
This tool is under the MIT License so feel free to use them in your projects! (if you're feeling a bit generous please credit me as well. 😃)