Jekyll site that worked well on Local doens't show up on Github Pages

Question

I did the follings:

1. made my username.github.io repo
2. cloned that repo to my local folder
3. In local folder, I did "jekyll new ..." to generate jekyll things
4. I modified "Gemfile" and "_config.yml" to use a theme named "minimal-mistakes" (added a line gem "minimal-mistakes-jekyll" to my Gemfile and "bundle install", then modified "_config.yml" to contain theme: minimal-mistakes-jekyll, then "bundle update")
5. typed "bundle exec jekyll serve" on terminal, go to localhost:4000, then my simple jekyll site showed up

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Then I pushed the local's change to remote server, and hoped my jekyll site show up when I enter my "username.github.io", but when I enter, the page is blank. nothing.

Well, is this because In local, I installed things by "bundle install" or "bundle update", but the github doesn't install things for me automatically?

How can make my username.githhub.io to show a theme-installed page?

+1 question: I did "jekyll new ...", in order to generate Gemfile and other jekyll related files, but this seems unnecessary. Just making a directory and make Gemfile and _config.yml file inside the dir by myself would work?

Answer 1

I guess I know why.

https://help.github.com/en/articles/adding-a-jekyll-theme-to-your-github-pages-site#adding-a-jekyll-theme-in-your-sites-_configyml-file
looking at #4, there are github-pages-supported themes and other themes that are not supported. for those not supported, you have to write remote-theme: ... to _config.yml, not theme: ...

Well, is this because In local, I installed things by "bundle install" or "bundle update", but the github doesn't install things for me automatically?

I think what I guessed is right.