I also run everything with docker stack(s) currently. Not using salt and haven’t heard of it. Why would I want salt and not ansible or something similar?
Salt (https://saltproject.io/) was an almost-winner around the time that Ansible blew up. It's pretty irrelevant nowadays since terraform and kubernetes - but still it's a very very good tool.
I'd suggest if you already know Ansible then don't change. If you have no idea which is which then try them both and let us know :)
The reasons that I used it were because the agent (called “minion”) initiates a connection towards the master, which can be handy if you’re behind NAT- but it was interesting to us because incoming connections are easier to manage at scale than outgoing ones.
Another reason was that the windows support was much more mature (though not perfect) and our environment was mostly Windows servers.
That said, installing the minion agent was easy, much easier than enabling winrm.
If you have sunk significant time into ansible I wouldn’t recommend switching, but it’s definitely not dead as per the sibling comment, I personally found it more enjoyable and easier to work with once understood the DSL pattern and added a few custom modules, it’s very simple underneath.
I'd suggest if you already know Ansible then don't change. If you have no idea which is which then try them both and let us know :)