Using Rpi4 with OH3 where there are a few Shelly’s installed (thus the binding) and working.
According to https://www.openhab.org/addons/bindings/shelly/doc/shellymanager.html: The Shelly Manager is a small extension to the binding, which provides some low level information on the Shelly Devices, but also provides some functions to manage the devices.
but whatever (IP or mDNS) I try with http://:8080/shelly/manager it throws an 404 error.
There is no Shelly manager binding.
The manager is not available in 3.0.x release, only since 3.1 M3(M4) or the dev version linked in Shelly Binding thread…