Is there a guide to help developers of mobile apps write an app that can take LTC as payment for virtual items? If not, what’s stopping us?
You can go through this by using btcpayserver, either on your own installation or by using a hosted service by a third-party.
On bititrain.com we went by the option to develop our custom solution (when btcpayserver was not yet a thing), and we will soon start to offer btcpayserver as a service.
or use payment gateways like NOWPayments, integrate via API, invoices, widgets or crypto buttons