I think using a dedicated NFC or RFID reader might be overkill. There’s an app for connecting NFC tags to Hass.io scripts. It’s super simple. Install the app, setup the config with your home assistant, then program the NFC stickers. I use the stickers for locks and doors, I even painted over them and they still work. I’ve only tried it on Android, so I can’t speak to the iOS version. I’m using Nabu-casa for external access, but at one point i had it connected to a duck DNS url - but i don’t think you’d need even that, because presumable you’d be connected to your home network when you were locking/unlocking at home.
Here’s the app:
https://play.google.com/store/apps/details?id=com.gerbenbol.hassnfc
Here’s a thread about it:
Hass NFC - Control Home Assistant with NFC tags
Here’s some NFC stickers that I got on Amazon. (You can get them even cheaper from Aliexpress)
https://www.amazon.com/gp/product/B075CFXY8V/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1