What evidence have you found so far? Where is it listed? Why are you asking?
The claim that freedom and equality are irreconcilable is not uncommon, Nikolai Berdyaev said "freedom is the right to inequality" (Свобода есть право на неравенство). It seems like a fairly obvious observation.
My replies to these questions:
1. "What evidence have you found so far?"
I have asked the question simply because I could not find any direct and reliable evidence that Solzhenitsyn had actually written or said the words that figure in the poster above.
2. "Where is it listed?"
When performing a Google search, the quote appears in many sites, most of them being sites specialized in quotations (which might simply repeat on and on the same initial misquotation).
3. "Why are you asking?"
I asked because in a few cases, the mention "possibly misattributed" (or something similar) was attached to the quote.
Given I'd like to re-use the quote, I wish I could cite it right. Otherwise, I would not cite it, or attribute it to Solzhenitsyn.
Since my initial posting, the only apparently reliable quote from Solzhenitsyn I have found so far on the same topic is from a speech he's reported to have given, apparently in French, on Saturday September 25, 1993, at Lucs-sur-Boulogne, France, at the inauguration of the "Historial de Vendée" (an event thus related to the memory of the War in the Vendée;
https://en.wikipedia.org/wiki/War_in_the_Vendée):
"La Révolution française s'est déroulée au nom d'un slogan intrinsèquement contradictoire et irréalisable : liberté, égalité, fraternité. Mais dans la vie sociale, liberté et égalité tendent à s'exclure mutuellement, sont antagoniques l'une de l'autre! La liberté détruit l'égalité sociale - c'est même là un des rôles de la liberté -, tandis que l'égalité restreint la liberté, car, autrement, on ne saurait y atteindre. […]"
(Literal English translation

"The French Revolution developed in the name of a motto that was intrinsically contradictory and unrealizable: liberty, equality, fraternity. But in social life, liberty and equality tend to exclude each other, are antagonistic of one another! Liberty destroys social equality – here is even one of the roles of liberty –, whereas equality restrains liberty, for one would not be able to reach it otherwise. […]"
This speech is extensively given at
http://la.revue.item.free.fr/nouvelles_de_chretiente141_090808.htm
I therefore suspect the quote that is the subject of this thread may represent a simpler and more compact rephrasing of the view expressed by Solzhenitsyn in this 1993 speech. I have however no proof of that. Of course I may be lacking more information, and I hope contributors to this thread may shed light on the topic. Many thanks in advance.