..good but this doesn't support all altcoins
I think there's no single exchange platform that supports all cryptocurrencies listed on CMC, it might even Binance, they don't list all altcoins on the market cap so there's no chance that you will find one exchange that supported all altcoins.
As already suggested already above,
Bisq and
Uniswap are the most common open-source decentralized exchange. Here's another one,
HollEx Kit exchange it seems I heard this but I don't have any personal experience it, so better to find your own way.
If there's centralized exchange open-source might vulnerable to hack and the reason most of them DEXs will survive in the trading business field because hacks and cheat are far away from them.