Thanks to Rob Inman for sharing this link over on Discord. They have an RS-232 to WiFi module available, based on the ESP8266 module. They chose to include my pre-configured fork of Bo Zimmerman’s ZiModem (with the settings for standard RS232 rather than Commodore serial). Cool.

https://www.simulant.uk/shop/retro-vintage-computer-wifi-modem-rs232-serial-hayes-compatible