Plenty of businesses sell through Facebook, WhatsApp or a phone call. There is no checkout page to integrate with, and there does not need to be.

Create a link with an amount, share it, get paid. You can cap how many times it is used and set a date after which it stops working, which is useful for limited runs and event tickets.

Invoices

Send an invoice and it moves to paid on its own the moment the payment lands and verifies. No reconciling a list of transfers against a list of invoices at the end of the week.

Both show up in the same dashboard as everything else, so your reports stay complete regardless of how the money came in.