I'm not sure that's a good move since all those companies have nothing to do with the russian army and the russian government and even if all are really russian.
I think the idea of boycotting Russian gambling platforms was to decrease income tax Russian Federal Reserve get. It would be logical, if all the taxes from gambling would got on military needs. But is not how real situation is.
I am not even sure, that all the casinos from the list on first page are registered on Russian territory. Maybe only part of them are. While the other is registered somewhere on Malta, BVI or Belize for example.
It would be fair to boycott national or state companies. But right now OP call to boycott random Russian gambling platform owners, random people.
Why not then boycott Russians famous vodka Stolichnaya? Russians do like vodka after all. But wait, Stolichnaya belongs to Stoli Group USA, LLC, New York, NY.
And this is the problem with those ‘sanctions’, as you have stated it is fine to sanction the government of Russia or the politicians at the very top which are directly responsible of the horrible events we are witnessing at Ukraine, but a random Russian person or business does not have much to do with the war at all and maybe they are even against it in principle, so something like this is simply too much in my opinion.
"Sanctions here, sanctions there, sanctions everywhere". Do they really help? Do they have any effect now ? Yes, now, because later it will be an effect on Russia, but the war needs to be stopped now, not later.
Our country has proposed sanctions and is trying to replace Russian gas. Yes, we are showing those Russian how bad they are, we will force them to stop, they will suffer from sanctions. But will they really do? So far I see how petrol price gained 10 cents every 12/24 hours. It cost 60 euro to fill full tank in January, it cost 100 euro to do the same now. Even though we had gas reserve, today I have received February utility bill with corrected heating column; +50 euro. I usually spend 50-70 euro to buy food for whole week. Two days ago I have refused to buy several goods, and had left +100 in the store.
2 weeks of war and sanctions against Russia, but my wallet suffered 150 euro loss. As if I am punishing myself. Same will be with boycotting their gambling platforms. We boycott them, and other platforms will get our money. If this is like that, is that boycott really that necessary?