Yup that's for containers. It looks like development sorta died on it but I think they will circle back once infrastructure work has been done for sync.
For proxies you can use whatever vpn service or plugin[1]. I use paid Nord because I need consistent access to certain countries for testing. There is some tunnel bear/Nord like plugins that have lists of free proxies.
1. https://addons.mozilla.org/en-US/firefox/addon/proxy-switche...
At least that's for controlling them easily. I use it for Whatsapp web on 2 accounts