First, if you want to exchange crypto for fiat it's not possible to do this in a decentralized way. If your concern is KYC then some options are more private than others.
There is always the option of using a major exchange like Binance and Kraken, but there will be quite a bit of verification involved here.
Other option is to do this peer-to-peer (P2P) where there will still be KYC (in most cases) but this is enforced by the sellers more than by platform itself. A lot of KYC requirements imposed by traders also depend on local laws so they vary from country to country.
This is a good list of P2P exchanges today but new ones are coming out every day.
Major exchanges are supporting P2P now too, but number of scams in some of them (eg. Binance) is a lot higher and this may have to do with lack of KYC requirements so it's worth keeping that in mind. Finally, it's worth checking if trading platform is non-custodial which means you have control of your funds in case platform goes down or blocks access for whatever reason. Few examples of non-custodial platforms: localcryptos, p2pmoon, localcoinswap. Localbitcoins on the other hand isn't one.