One historical fact does come to mind: the St. Petersburg stock exchange reopened in 1917 (after being closed for world war 1), then closed two months later because of the Russian Revolution. It did not reopen and shareholders of Russian stocks lost everything.
I don't see something like that happening today. But what if Russia confiscates the shares of foreign shareholders?
And Ukraine might not exist as a country soon.
> Don't put any money into both stock exchanges right now, especially the russian one.
Then you are asking what money would go into Russia...
I mean if you have the money and confidence by all means, take the gamble, but keep in mind it's a gamble. Don't sell your house, don't spend your reserves, don't bet everything on one horse.
If you want to play on the effects of the conflict, either buying or shorting the ruble is the best way to go.