...As such it was difficult to update.
ShadowsocksX-NG has just a copy of ss-local from Homebrew, and its GUI code has been rewritten in Swift. It now runs as a background service rather than an in-app process, so the ss-local may still be running even after you quit the app.
ShadowsocksX-NG also has an added manual mode so you can configure your apps to use the socks5 proxy manually without configuring the system proxy settings.