Let me give you an example, let's say I have sellers and buyers on my site. Something costs 100 altcoins, when buyer wants to buy that one thing, I split payments between me and seller. I send 10 altcoins to my address and 90 altcoins to seller's address.
The same with tipping, when user A wants to tip user B with 100 altcoins, 10 altcoins goes directly to my crypto address and 90 altcoins goes directly to user B's crypto address
BTCpayserver would be the best option as suggested above but they are only supported limited coins mostly it only support BTC but if you are looking for an altcoin payment gateway I think you would need something like a Binance merchant but I don't know if they support adult website you can try contacting them.
Take a look at this
https://merchant.binance.com/enOr if you are looking for more supported coins check these two crypto.com and mycryptocheckout.com