How do I keep an interface in sync between multiple components without poly tool?
One of Polylith's most important value add is the tool. Why do you want to not use it? Sounds like you'd need some kind of tool anyway
I may want to utilize polylith architecture in languages that don't have the tool.
I'm not sure you'll find a way to keep components implementing the same interface in sync without some kind of tool. I'd say there's also a good chance that those tools will be separate per language