LINQ-inspired recursive file search
As someone who's been writing cross-platform tools on .Net Core, this doesn't do what I expect it to do. 


finder.TargetDirectories.Add("/src");



I expect that to target a directory named src at the root of the file system. On Linux: /src; on windows C:\src. It would be more clear if the user passed in a relative file path or a complete file path. 

Also, please don't concatenate file paths this way. 


$"{path}/{new DirectoryInfo(subDir).Name}"



This is terribly error prone. It's hard to get right the first time and it's even harder to refactor later. Always use System.IO.Path.Combine().