I'm wondering about the Strike app also that twitter is using. My guess is that none of these apps actually handle keys, and the backend is an exchange using lightning network.

I've always seen the lighting network as a not great solution unless it is used between exchanges (think Coinbase <-> Binance). If it were to be used by users directly, you'd still have to pay the user-cost of receiving enough (takes time) and then establishing a channel.

Yeah, it rocks!! Love Lightning. I send sats to friends and family who can exchange them for goods and services in their local currencies. It’s almost instant and very low or zero fees.

I recommend checking out BTCPay server, it is a full BTC node, LN node and payment invoicing system. Integrated into e-commerce platforms and apps.