I do not really believe that counting cards without a physical deck (without swapping the deck for a new one, as they do in physical real world gambling casinos).
The online version of card counting does not exist due to how much easier it is to install certain security systems in place to make card counting impossible. Although I could not tell you what those security measures look like. And even if you somehow did succeed because you found a loophole in their algorithm or something, you would still be faced with breaking the terms of service and getting your account and funds frozen...
It all goes down to the Casino's suspicion. A player can be charged with card counting even though he doesn't do it and a player cannot do anything about it. Most of the detection is probably done through software and application so mostly if they found a player winning continuously, the player can be tagged with card counting whether the suspicion is true or not. That is somehow unfair but well, the world is really unfair so nothing a player can do about it. Even if he often disputes against the casino or live game provider, he cannot prove that he is not card counting. The decision and authority is on the game provider so there is nothing for a player to do but to follow the Live game provider's verdict. The player has nothing to lose but access since in most cases, the player can withdraw his funds.
Here the question is, have you ever seen a user getting banned from an online casino for card counting?
To be clear, card counting isn't a method to always win, it's just a method to have better odds.
I think this is not possible because how can the dealer see you? Unless if it's a live game where they can also see your face in real-time. There are people who got banned in online casinos but that must be for other reasons. This is one of the advantages of the online casino, that is we can do something which we normally can't do in the real life.
The game provider has an application running in the background that analysis a player's action. From that they can determine whether a person is card counting or not. It maybe sounds absurd by no one can refute the method because it is the game provider's right to accept, denies, or kick players in their game session.
Winning from this trick is not guaranteed so risking yourself in a real-life casino is not recommended but if you are only playing online then it's a must to include every time you play a certain card game. Having an increased chance of winning is always better than the standard winning rate.
I would rather have a standard winning rate than be suspected of card counting. Card counting is also frowned by online casinos and they have software and apps for detecting it. Though we don't know how accurate this software detection is, we should always take into account that Card counting is one of the prohibited techniques stated on the TOS of gambling game provider.