I'm helping our local Fablab to manage physical access with a series of ESP8266 and esp-rfid https://github.com/esprfid/esp-rfid/ (of which I became maintainer. If you want to use it as well I can help!)
Extra bonus points for support for real commercial readers using OSDP’s transparent mode or whatever they call it these days. As I understand it, an early standard involved a horrible hack that was so horrible that HID managed to patent it, but the protocol was redone to avoid being a horrible hack, and the new version is also unencumbered. Although maybe the spec costs $30.