https://reprap.org/forum/read.php?13,216927,217155
$15 serial to wifi module HLK-RM04
This page has some good infos [www.aliexpress.com] Someone swapped out the firmware [forum.openwrt.org] Here's a little easier to order version on dx.com...
serial to wifi15modulehlk
https://hackaday.io/project/161491-qmesh-a-lora-based-voice-mesh-network/log/194667-esp32-serial-to-wifi-bridge-complete
ESP32 Serial-to-Wifi Bridge Complete | Details | Hackaday.io
serial to wificomplete detailsesp32bridgehackaday