The problem with dubbed is if they are officially available? you can check out this x265 german site (not sure if they are dutch dubbed). the download link is not showing for me so you have to ask them directly.
If you mean for downloaded .mkv (or whatever) files?
Your best bet would be to find a source with any audio track you need, extract it and remux it with your favorite source/group release.
But that is work intensive.