For payments we use our own hosted BTCPay server. All payments through it are secured and if something goes wrong during payment, we will resolve the issue with you (either by refunding you or manually creating the order). Our BTCPay server allows you to pay with Bitcoin (On-Chain) and the Lightning Network (Off-Chain).
Altcoins are accept via SideShift.ai, which convert most alt coins to Bitcoin for you (and charge a small fee to do so). They do require a minimum amount to convert, so this option might not always be available. If you have any question about SideShift, checkout their FAQ page.
Coins of Nakamoto cannot be held accountable for any issues that might arise whilst using FixedFloat, as it is a third party we have no connection to.