Shameless plug: We (mitmproxy) have a somewhat reasonable web UI (React/Typescript), but I think there's a lot more potential here. We're also looking for Google Summer of Code students at the moment, so if someone wants to spend a few months hacking on cool FOSS stuff while getting a nice stipend for it, please check out https://github.com/mitmproxy/mitmproxy/issues/5048 and reach out to me. I'd love to work with good front end folks on this! :)