Privacy sidechain? Liquid network might be what you're looking for since they implement Confidental Transaction. For something easier or lighter on Bitcoin on-chain, MimbleWimble or other form of non-interactive CoinJoin probably are better option than CT.
Litecoin, which signaled MWEB into activation in May 2022, has always been something of a test environment for features later implemented in Bitcoin. Litecoin was the 1st to have SegWit, a Lightning Network, and now MWEB, which is an optional privacy enhancing feature, used by Grin as default.
Here's a pretty in-depth article about how it all works. I honestly don't see why this can't also be integrated with BTC, if miners signaled for it... maybe there's a good reason but I don't know what it is.
