@dangen-effy Your local server running the UI should be the same as before https://localhost:8080. If you are also running a full Jitsi stack locally (not likely) then thats the address you need to put in process.env.WEBPACK_DEV_SERVER_PROXY_TARGET
Typically people run their own Jitsi stack on external development server(s) and point their local computer to that.
If you want to do development of the UI on the same server as your Jitsi server (Prosody, Jicofo, JVB etc), read this topic
When i put WEBPACK_DEV_SERVER_PROXY_TARGET as https://localhost:8080 while running local backend components, front page renders Error occured while trying to proxy to: localhost:8080/