I was also looking for a cryptocurrency exchanger recently as I needed to transfer Dogecoin (DOGE) to Litecoin (LTC). According to my personal observations, the most favorable conditions for exchanging cryptocurrencies are here
https://alligat0r.com/coin-pairs/doge/ltc/info. And there is the possibility of exchanging at a fixed or floating rate. In general, as far as I understand, this is an aggregator of cryptocurrency exchangers, and with its help, you can see exchange rates in almost all cryptocurrency exchangers. and already choose an advantageous offer on your own.