This!! you can use btcpay server, and create a store account. Then you can generate a pos button url so customers can pay with btc onchain or lightning. For example I created a POS payment button web app, so a merchant can set up an account in a btcpay server (a server of his own or a server from a trusted friend, relative) And install the configured app in his/her pos devices or mobile phones and charge with btcpay with ease (selecting any fiat reference he wants)