MacOS下安装Rails遇Ruby LoadError问题求助

我已经翻遍谷歌找解决方案了，麻烦别直接甩谷歌前几条结果哈！之前一直在处理ruby 2.0 rails gem install error "cannot load such file -- openssl"这个问题，结果现在不管是执行gem install rails还是任何gem安装操作，都会弹出两个报错：

ERROR: Loading command: install (LoadError)
cannot load such file -- openssl
ERROR: While executing gem ... (NoMethodError)
undefined method `invoke_with_build_args' for nil:NilClass

更头疼的是，我用brew、rbenv、rvm反复安装了Ruby 2.7.1，但每次执行ruby -v，返回的始终是系统自带的ruby 2.3.7p456 (2018-03-28 revision 63024) [universal.x86_64-darwin18]。我知道Ruby版本低于2.4会和OpenSSL 1.1不兼容，而且安装Rails要求Ruby版本必须大于2.4.4，这就完全陷入死循环了...

下面是我执行gem env的输出结果，供参考：

[14:21:23] jasper.huang ruby-2.7.1 gem env
RubyGems Environment:
  - RUBYGEMS VERSION: 3.1.2
  - RUBY VERSION: 2.7.1 (2020-03-31 patchlevel 83) [x86_64-darwin18]
  - INSTALLATION DIRECTORY: /usr/local/lib/ruby/gems/2.7.0
  - USER INSTALLATION DIRECTORY: /Users/jasper.huang/.gem/ruby/2.7.0
  - RUBY EXECUTABLE: /usr/local/bin/ruby
  - GIT EXECUTABLE: /usr/bin/git
  - EXECUTABLE DIRECTORY: /usr/local/bin
  - SPEC CACHE DIRECTORY: /Users/jasper.huang/.gem/specs
  - SYSTEM CONFIGURATION DIRECTORY: /usr/local/etc
  - RUBYGEMS PLATFORMS:
    - ruby
    - x86_64-darwin-18
  - GEM PATHS:
     - /usr/local/lib/ruby/gems/2.7.0
     - /Users/jasper.huang/.gem/ruby/2.7.0
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => false
     - :bulk_threshold => 1000
  - REMOTE SOURCES:
     - https://rubygems.org/
  - SHELL PATH:
     - /Users/jasper.huang/Documents/School/USC/SPRING20/CSCI310/Project2/google-cloud-sdk/bin
     - /Library/Frameworks/Python.framework/Versions/3.7/bin
     - /usr/local/CrossPack-AVR/bin
     - /Library/Frameworks/Python.framework/Versions/3.5/bin
     - /usr/local/bin
     - /usr/bin
     - /bin
     - /usr/sbin
     - /sbin
     - /usr/local/share/dotnet
     - /opt/X11/bin
     - ~/.dotnet/tools
     - /Library/Frameworks/Mono.framework/Versions/Current/Commands
     - /usr/local/CrossPack-AVR/bin
     - /Applications/Xamarin Workbooks.app/Contents/SharedSupport/path-bin
     - /Users/jasper.huang/.rvm/bin

内容的提问来源于stack exchange，提问作者Jasper Huang