Evidence? Not that's been publicly released, at least. Suspicion? Yes.

They have the subs to do it: https://www.thedrive.com/the-war-zone/9928/russias-massive-a...

and there've been suspicious cuts: https://www.thedrive.com/the-war-zone/43828/undersea-cable-c...

It's undoubtedly something they'd (and all the other major powers) plan to do in a wartime scenario.