Lnbits makes it pretty easy. You just need an ESP32 board ($10+usb power supply) and a cheap relay ($5) then to create a static LNURLp QR code to stick on the arcade machine (specific QR per arcade machine or per coin slot for arcades where slots are specific to each player) . There's even a way to provision the ESP32 directly from a web browser (no arduino ide required). Then when someone pays the LNURLp QR, the ESP32 picks it up and triggers the coin mech switch in the arcade.
A couple of potential issues:
. LN wallet compatibility with LNURLp
. Lnbits maintenance windows (affects uptime)
. LN liquidity issues/channel balancing yada yada
It is also not too hard to roll your own to avoid the Lnbits dependency and if you are ambitious you can add a display into the mix to avoid LNURLp compatibility issues. A new invoice could be displayed on the screen each time for just normal vanilla LN.
Feel free to DM me or just keep this convo going. I've always wanted to open my own LN arcade so happy to help. Sorry for the delay. Been off nostr a few days. Thanks for tagging me, Lou!