If you're genuine in asking for proofs, don't s*ge please.
The proofs are in the reports of the actual attack and the video footage which demonstrates 2 impacts, with some debris*. 2 impacts out of 15 launched SCALP missiles and numerous MALD and HARM missiles deployed in a mass attack. That's 13% success rate for the Storm Shadows, which is a 87% kill score for Russian air defense. The actual target was the shipyard itself, as that would a critical hit indeed, limiting repair facilities and production facilities of the Russian Navy.
*The impacts are not full on hits, had the cruise missile actually directly hit the Corvette the damage would have been significantly higher, the 2 missiles that hit were likely clipped by SAMs but were still flight capable enough to roughly reach target coordinates.
The damage looks bad visually, but if you've ever seen footage of WW2 destroyers in Dry Dock, you'll see that this is essentially surface damage, not a write-off of the ship. It was essentially nil. The repairs of the Askold will be pricey, at least several million dollars to replace the damaged RADAR array, siding and burnt sections, but considering that each Storm-Shadow is priced at 3 million dollars each, the ADM-160B MALD is 120,000 dollars each and that AGM-88 HARM missiles are 284,000 to 847,000 dollars each + fuel expenses for putting that many Su-24s and MiG-29s into the air (the Su-24 can only carry 4 Storm Shadows at a time, so that's a minimum of 4 Su-24s + escort and decoy launches) means the combined cost for the entire operation is going to be roughly the same as the cost of repair for the ship, making it a pyrrhic victory for Ukraine at the very least.
Ukrainian telegram channels actually claimed 18 Storm Shadows were launched and 3 hit the ship, but the Russian MoD stated otherwise and someone anonymously released footage before that where only 2 impacts are seen. https://www.rbc.ru/politics/05/11/2023/6546b4e69a79477298bac1f8https://svpressa.ru/war21/article/393621/