This article its about private proxies, not free public proxies. There are many companies that are offering free public proxies and there are also around 20 companies that are offering private proxies.
For private proxies you should try SSLPrivateProxy. I have 200 Instagram private proxies with them since a few months ago and I'm 100 percent satisfied. For free public proxies you should try HMA. They have a list of public free proxies updated daily.