Since you mentioned "simple" in your subject field, I would suggest "Blockonomics ^{[non-custodial]}" but if you want the best and you're willing to deal with having a complex setup process ^{[more control]}, go with "BTCPay ^{[self-hosted]}".

Most users ^{[including me]} wouldn't recommend their services ^{["here's why", although it's a little bit outdated]}.