Hi ! =))
I’m sorry for a delayed reply, unfortunately you are right, they nearly do not exist, the professional grammar lessons/courses of Russian on the Internet, as they are only after money in this country these days, the less professional the instructor is, the more money they ususally require! =)))
I think I have an example of really serious grammar lessons, but unfortunately I will be able to just provide a sort of sample to have an idea of the professionalism level of their approach to Russian grammar…
And, yes, saying "professional’ I do NOT imply it’s smth like purely theoretical; no, the opposite is right, it’s very much practical course of grammar! =))) I’ll find a link for the videos, and post it here! =))