The Bundler 2.3 announcement includes context and a more detailed explanation of the changes in this version. This is a summary of the biggest changes. As always, a detailed list of every change is provided in the changelog.
Bundler is now able to lock itself! The Bundler version used to
create Gemfile.lock will be used for all future runs of
bundle install. Upgrade Bundler for your app by running
bundle update --bundler. (Requires RubyGems 3.3 or
higher.)
Bundler 2.3 also includes other improvements like enhancements
bundle gem or bundle add, and deprecation
messages to make dropping support for old rubies in the future
smoother.