According to the Silmarillion, orcs are a corrupted race of elves, either bred that way by Morgoth, or turned savage in that manner. The Dark Powers tortured, corrupted and bred the captive Elves until they became the vile Orcs.

Elder Scrolls orcs are very close to this version. They were changed when their god Trinimac was eaten by Boethiah, turning him in to Malacath and all of Trinimac's elven followers in to orcs. Except in this case they're still just regular people who have some large-scale bad luck and have often been discriminated against, there's not anything evil or corrupted about them

Isn't there a famous note, that Christopher found after publishing the Silmarillion, that says "Not Elves"?

That was one of the initial ideas Tolkien had, and that also made its way into final Silmarillion edition after his death. However, there are notes from later years where its shown he has changed his mind about Orcs elven origin. Also, due to his Catholic upbringing he had struggled with the idea of an intelligent race so corrupted to be irredeemably evil and undeserving of mercy.

In later material the Orcs had been either former humans tortured and deformed by Morgoth/Sauron, or, even later on, automatons possessed by fallen spirits and/or imbued with Morgoths evil will (as only Eru was capable of creating true life, so technically the Orcs would not be real living beings), thus skirting around the intelligent being issue.

Of cource, the Silmarillion does not reflect that, as the released book is based on older material, so in the end, the elven origin of Orcs IS sort of canon, at least as much as anything is, with JRRT constantly changing things.