Apps to use in Prague: Qerko. You can pay in many restaurants & cafés with bitcoin through the Qerko app. When you see the logo & QR just like on the picture, you can pay with bitcoin (LN) in that place.

Though one recommendation: don't ask the staff about a bitcoin payment, they might not even know that Qerko allows bitcoin payments! The way to do it is you set up the bitcoin payment option in the Qerko app on your phone, and then you can proceed with payment (the restaurant receives fiat on their end).

Here are the links for App Store and Google Play: