Sorry, I rarely use Taobao mirrors so I don’t know what happened. The administrator of this mirror is in the ruby China community, you can ask. As a programmer, it is very important to surf the Internet scientifically.

Also, if you start learning sass now, I advise you not to learn compass. This project is no longer going forward because having a library as large and comprehensive as compass has proven to be a wrong design choice over the years.

So you don’t have to use ruby. For example, you can use node-sass, which is faster than ruby sass (it supports slightly less sass functions, but it does not hinder normal development and will be continuously upgraded)

For the supported tools, you can learn bourbon, neat, susy, breakpoint... etc. Don't learn big frameworks, learn components, and learn to implement some common patterns by yourself. This is the right way.

You should make sure you have only one ruby source. When you remove the official website source, you should pay attention to whether there is a/， 比如你用gem sources --remove https://rubygems.org/时是不能移除https://rubygems.org这个源的，只能移除https://rubygems.org/这个源，我之前使用openSUSE时是这样的情况。
你也可以尝试使用中科大的rubysource at the end of the URL. Modify the mirror source in Linux to speed up downloading (pip-RubyGems-NPM-Docker)