The sanctions are nothing to them.
They've already made their own rule for the countries that they're dealing with and it's in favor of them. So all of the people that boycotts them or not, they won't care.
You decide if all casinos based on Russia will be boycotted by you or you don't do anything as that doesn't concern you and they're just businesses that are residing there and as well as affected by the war.
Economic sanctions alone are not effective, let alone boycott gambling sites originating from Russia, it is even more ineffective.
sanctions will be effective if the country that is subject to sanctions, has weaknesses (depending on other countries) while so far the boycott and sanctions imposed on Russia are not effective at all because they know that foreign countries need their gas and oil.
There have been some initiatives from a few countries in Europe,mainly UK and Germany have said that they will honor the contracts already signed for oil with Russia but they will look for alternative ways and all EU wants to find that greener energy which will remove their dependency from Russia.While sanctions may not work for the government of Russia surely they are devastating to the civilians of Russia as they already are starting to feel consequences,no one likes them anymore guilty or not,no dollar or euros can be used by them and the list will go on,everywhere they go they will be seen as some "unfriendly humans" that no one cares.They are already having troubles with payments as a friend of mine told me he was asked for help to exchange crypto here in our country for them in US dollars and to keep them for them,of course this was a big NO from my side and that is going to be the answer forever to any help request coming from them.