Can you count cards at live online casinos?
Theoretically you can, yes. If you manage to find a live casino that offers blackjack with a single deck or without any re-shuffling, then you will be able to use a system like high-low.
Truth is, training to do this at live casinos is quite the perfect solution to get very good. There’s no stress and you can use a pen and a paper until you are good enough to do all the counting in your head.