linter-julia is actually not in Juno’s ecosystem at all – its implementation is pretty old and imho I don’t recommend using it for now.
We’re planning to implement our own linter based on CSTParser.jl, but it’s not our top priority and so I can’t provide an estimate.
So in conclusion there is no (static-)linter in Juno for now, but with Juno’s interactive code execution feature you can easily find syntactical misses. If you really want a linter, vscode-julia extension will do that fine.