You can accept cash payments for in-person meetings. To set this, no such any integration required.
You only need to enable it from settings of accept payment online.
Confirming cash payment
Go to My bookings in the left sidebar.
Click on meeting time link for which you want to confirm payment.
Right side pane will appear. Click on Confirm payment button.
Add notes if needed (optional).
Click on Confirm.
Once confirmed, the payment status will be updated to Paid for that meeting. You can also view successful payments in the Payments section.