I guess mimble-wimble could be considered because it's already working in Litecoin that has similar code like Bitcoin, bit it is arguably inferior to Monero.
Problem is that adding mimble-wimble or any other privacy related code change would probably create new Bitcoin fork and drama in community, but maybe that is not such a bad thing.
It could be possible to create some second layer network that would have full privacy working on top of Bitcoin, but I didn't see anything like that getting any tracking.
You can see most privacy based altcoins on Coingecko page, but most of them are centralized junk with no real development:
https://www.coingecko.com/en/categories/privacy-coins