The questions we must ask now is...are they biased? Since Binance is always #1 with a perfect score. Are they trying to eliminate competition? etc.
Sometimes, Coingecko take down Binance from the first on the list. There was a time that I checked that Binance.US was even above Binance.com on Coingecko while Binance.us was not the first on the list. But Binance.com appears more as first on the list.
https://www.coingecko.com/en/exchangesCoinmarketcap is owned by Binance. Binance bought it like 3 years ago which I think you knew about. That alone can make them partial.
Check out the list below:
list of CEX and Dex exchanges it comprises of both CEX and Dex on the decentralized exchange role you will see list of Decentralized exchange's. But I will highly recommend Bisq, as most members have recommended it in the past. Others in the list I don't know how updated they are now since their has not been update from the OP since.
He should not depend on that link, it was posted in 2018 and there have been a lot of changes. There are some exchanges that are there but not recommended anymore.
I will recommend
https://kycnot.me/. But some of the exchanges like Kucoin are centralized, not decentralized but not require KYC. Because they are centralized, they can force any of their users to do KYC at anytime. Kucoin even now require KYC He should use those with the score of at least 9.
For decentralized exchange, I will recommend Bisq. But it has just few (not many) trading pairs but it is the best bitcoin decentralized exchange.
For altcoins, he can decide to use those exchanges that you can connect directly to your altcoin wallet:
https://coinmarketcap.com/rankings/exchanges/dex/