Errors when doing Bundle Update - ruby-on-rails

Question

I updated my ruby to 3.0.0 but for some reason now my application doesn't work. I have searched online for different answered but I cannot find anything. This error has gotten me going crazy now. Here is what happens.
When I do bundle update I get:
Bundler could not find compatible versions for gem "ruby":
In Gemfile:
ruby (~> 3.0.0)
thredded (~> 0.16.13) was resolved to 0.16.16, which depends on
ruby (~> 2.3)
I looked online and someone said to do bundle update rails but when I do I get this error:
Bundler could not find compatible versions for gem "activemodel":
In Gemfile:
active_model_serializers was resolved to 0.10.10, which depends on
activemodel (>= 4.1, < 6.1)
challonge-api was resolved to 0.2.0, which depends on
activeresource was resolved to 5.1.0, which depends on
activemodel-serializers-xml (~> 1.0) was resolved to 1.0.2, which
depends on
activemodel (> 5.x)
challonge-api was resolved to 0.2.0, which depends on
activeresource was resolved to 5.1.0, which depends on
activemodel (>= 5.0, < 7)
carrierwave was resolved to 2.0.2, which depends on
activemodel (>= 5.0.0)
rails (= 6.1.2.1) was resolved to 6.1.2.1, which depends on
activemodel (= 6.1.2.1)
Any ideas what I need to do?
Here is my gem file:
source 'https://rubygems.org'
ruby '~> 3.0.0'
Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '6.1.2.1'
Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0.0'
Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
Use jquery as the JavaScript library
gem 'jquery-rails'
gem 'merit', '= 3.0.1'
Used to implement at.js for auto complete mentions/emojis
gem 'jquery-atwho-rails'
Use twitter bootstrap sass
gem 'bootstrap-sass', '~> 3.4.0'
gem 'autoprefixer-rails'
gem 'font-awesome-rails'
gem 'font-awesome5-rails', '~> 1.0', '>= 1.0.1'
gem 'font_awesome5_rails'
gem 'xbox_live_api'
gem 'faraday'
gem 'oj'
gem 'thredded', '~> 0.16.13'
gem 'rails-ujs'
group :development do
gem 'spring'
gem 'letter_opener'
gem 'guard'
gem 'guard-rspec', '~> 4.2.8'
gem 'byebug'
end
group :development, :test do
gem 'puma'
gem 'sqlite3', '~> 1.3.6'
end
group :production do
gem 'pg', '~>0.18'
gem 'unicorn'
gem 'cloudinary'
gem 'rails_12factor'
gem 'fog'
gem 'fog-aws'
end
gem 'devise'
gem 'carrierwave'
gem 'friendly_id', '~> 5.0'
gem 'will_paginate', '~> 3.1.0'
gem 'public_activity'
gem 'acts_as_votable', '~> 0.10.0'
gem 'acts_as_commentable'
gem 'acts_as_follower'
gem 'counter_culture', '~> 0.1.33'
gem 'faker'
gem 'populator'
gem 'auto_html', '~>1.6.4'
gem 'sanitize'
gem 'active_model_serializers'
gem 'private_pub'
gem 'thin'
Use ActiveModel has_secure_password
gem 'bcrypt', '~> 3.1.7'
Use unicorn as the app server
gem 'unicorn'
Use Capistrano for deployment
gem 'capistrano-rails', group: :development
Use debugger
gem 'debugger', group: [:development, :test]
gem 'round_robin_tournament'
gem 'tournament-system', '~> 2'
gem 'challonge-api'
gem 'tournament'
gem 'oauth2'
gem 'activerecord-session_store'
gem "simple_calendar", "~> 2.0"

Answer 1

Currently Ruby 3.0 is not supported with Rails, as there will be next release for Rails. You can do following and it works by installing dev branch of ruby 3. I used ruby 3.1.0dev (2021-02-14T05:09:08Z master ff527e7e32) [x86_64-darwin19] Following commands are with RVM you can use same with other softwares I tried by installing
rvm install ruby-head
This command installed version ruby 3.1.0dev Now install rails
gem install rails
Now create new project
rails new test_rails
now run it using rails s' if you are getting error that ruby version 3.1.0 required is because rails has added this in .ruby-version` so it is just warning no issue. You can try latest version but as I said it is dev version not stable. Note ruby-head will keep changing version of ruby installed as it is latest version. And good news it is blazing fast! I love it.
I suggest use ruby 2.7.2 with rails 6 till new release comes, the above is for test purpose only, not production or actual product. You should use ruby 2.7.2 for production or product.