Hi Ivan,
No extension support. As Martin says, it is a minimal browser. You can turn off JavaScript universally. You can have a list of blocked domains and good cookie management, I have cookie policy set to "Save Persistent Only" to avoid having to reenter credentials.
Eventually we might get a working falkon browser which does have a builtin ad blocker IIRC and they're planning on adding extensions.
The dependencies have become complex enough that no one has has the motivation to figure them out as using YUM is simpler.
If you don't like the idea of YUM/RPM being installed, you could just use it occasionally by removing the minimal stuff in config.sys and putting it in a cmd file so it only works in a cmd window. Mostly just %UNIXROOT%, LIBPATH (%BEGINLIBPATH%) and %PATH% should be good enough to run dooble.