WebBLE is experimental, works in Chrome, Chrome Android, and Edge (maybe Opera) and sometimes you need to enable experimental functionality. Google for web ble chrome enable, check other browsers for support.
Colleague of mine is using WebBLE in our company products so I wanted to show how easy and multiplatform it is to do a online webpage which could be some kind of companion "app" to your watches. I noticed that iOS doesn't have companion app yet.
I bought and use COLMI P8 with InfiniTime firmware. This page is using standard BLE Hour Service so this page could also work with other BLE devices. This code is quick'n'dirty proof-of-concept. I hope that someone will use this idea to create better application. Thanks to Javascript someone can in the future create a web page to load file from disk and do for example a DFU update or write a file or image to the SPI FLASH memory.