SSL errors on generating new Jekyll site, then subsequent SSL errors on gem install

Question

I can't get a new Jekyll site running on my local machine. The installation process itself seems to go fine, but when I try to run jekyll new, I run into SSL errors, which seems to brick any subsequent gem commands

Using macOS 10.15.7 and Ruby 2.7.5 with rbenv.

$ gem update --system 
Latest version already installed. Done.

$ jekyll new someblog
Running bundle install in /Users/my.user/someblog... 


Bundler: Fetching gem metadata from https://rubygems.org/..........
  Bundler: Resolving dependencies...
  Bundler: Using public_suffix 4.0.6
  Bundler: Using bundler 2.3.8
  Bundler: Using colorator 1.1.0
  Bundler: Using concurrent-ruby 1.1.9
  Bundler: Using eventmachine 1.2.7
  Bundler: Using http_parser.rb 0.8.0
  Bundler: Using ffi 1.15.5
  Bundler: Using forwardable-extended 2.6.0
  Bundler: Using rb-fsevent 0.11.1
  Bundler: Using mercenary 0.4.0
  Bundler: Using liquid 4.0.3
  Bundler: Using rouge 3.28.0
  Bundler: Using safe_yaml 1.0.5
  Bundler: Using unicode-display_width 1.8.0
  Bundler: Using pathutil 0.16.2
  Bundler: Fetching rexml 3.2.5
  Bundler: Using addressable 2.8.0
  Bundler: Using i18n 1.10.0
  Bundler: Using terminal-table 2.0.0
  Bundler: Using sassc 2.4.0
  Bundler: Using rb-inotify 0.10.1
  Bundler: Using em-websocket 0.5.3
  Bundler: Using jekyll-sass-converter 2.1.0
  Bundler: Using listen 3.7.1
  Bundler: Using jekyll-watch 2.2.1Retrying download gem from https://rubygems.org/ due to error (2/4): Gem::RemoteFetcher::FetchError SSL_connect returned=1 errno=0 state=error: certificate verify failed (Hostname mismatch) (https://rubygems.org/gems/rexml-3.2.5.gem)
  Bundler: Retrying download gem from https://rubygems.org/ due to error (3/4): Gem::RemoteFetcher::FetchError SSL_connect returned=1 errno=0 state=error: certificate verify failed (Hostname mismatch) (https://rubygems.org/gems/rexml-3.2.5.gem)
  Bundler: Retrying download gem from https://rubygems.org/ due to error (4/4): Gem::RemoteFetcher::FetchError SSL_connect returned=1 errno=0 state=error: certificate verify failed (Hostname mismatch) (https://rubygems.org/gems/rexml-3.2.5.gem)
  Bundler: Bundler::HTTPError: Could not download gem from https://rubygems.org/ due to
  Bundler: underlying error <SSL_connect returned=1 errno=0 state=error: certificate verify
  Bundler: failed (Hostname mismatch) (https://rubygems.org/gems/rexml-3.2.5.gem)>
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/rubygems_integration.rb:508:in
  Bundler: `rescue in download_gem'
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/rubygems_integration.rb:480:in
  Bundler: `download_gem'
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/source/rubygems.rb:527:in
  Bundler: `download_gem'
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/source/rubygems.rb:479:in
  Bundler: `fetch_gem'
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/source/rubygems.rb:165:in
  Bundler: `install'
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/installer/gem_installer.rb:54:in
  Bundler: `install'
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/installer/gem_installer.rb:16:in
  Bundler: `install_from_spec'
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/installer/parallel_installer.rb:186:in
  Bundler: `do_install'
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/installer/parallel_installer.rb:177:in
  Bundler: `block in worker_pool'
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/worker.rb:62:in
  Bundler: `apply_func'
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/worker.rb:57:in
  Bundler: `block in process_queue'
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/worker.rb:54:in
  Bundler: `loop'
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/worker.rb:54:in
  Bundler: `process_queue'
  Bundler: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/site_ruby/2.7.0/bundler/worker.rb:91:in
  Bundler: `block (2 levels) in create_threads'
  Bundler: 
  Bundler: An error occurred while installing rexml (3.2.5), and Bundler cannot continue.
  Bundler: 
  Bundler: In Gemfile:
  Bundler: minima was resolved to 2.5.1, which depends on
  Bundler: jekyll-feed was resolved to 0.16.0, which depends on
  Bundler: jekyll was resolved to 4.2.1, which depends on
  Bundler: kramdown-parser-gfm was resolved to 1.1.0, which depends on
  Bundler: kramdown was resolved to 2.3.1, which depends on
  Bundler: rexml

Not only does this fail, but I subsequently can't install or update any gems:

$ gem update --system
ERROR:  SSL verification error at depth 0: Hostname mismatch (62)
ERROR:  While executing gem ... (Gem::RemoteFetcher::FetchError)
    SSL_connect returned=1 errno=0 state=error: certificate verify failed (Hostname mismatch) (https://rubygems.org/specs.4.8.gz)

Restarting my computer fixes my gems' SSL issue, but then the issue pops back up if I try a new jekyll new command.

Here is my gem environment:

$ gem env
RubyGems Environment:
  - RUBYGEMS VERSION: 3.3.8
  - RUBY VERSION: 2.7.5 (2021-11-24 patchlevel 203) [x86_64-darwin19]
  - INSTALLATION DIRECTORY: /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0
  - USER INSTALLATION DIRECTORY: /Users/my.user/.gem/ruby/2.7.0
  - RUBY EXECUTABLE: /Users/my.user/.rbenv/versions/2.7.5/bin/ruby
  - GIT EXECUTABLE: /usr/bin/git
  - EXECUTABLE DIRECTORY: /Users/my.user/.rbenv/versions/2.7.5/bin
  - SPEC CACHE DIRECTORY: /Users/my.user/.gem/specs
  - SYSTEM CONFIGURATION DIRECTORY: /Users/my.user/.rbenv/versions/2.7.5/etc
  - RUBYGEMS PLATFORMS:
     - ruby
     - x86_64-darwin-19
  - GEM PATHS:
     - /Users/my.user/.rbenv/versions/2.7.5/lib/ruby/gems/2.7.0
     - /Users/my.user/.gem/ruby/2.7.0
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => false
     - :bulk_threshold => 1000
     - :sources => ["https://rubygems.org"]
     - :concurrent_downloads => 8
  - REMOTE SOURCES:
     - https://rubygems.org
  - SHELL PATH:
     - /Users/my.user/.rbenv/versions/2.7.5/bin
     - /usr/local/Cellar/rbenv/1.2.0/libexec
     - /Users/my.user/.rbenv/shims
     - /Users/my.user/.nvm/versions/node/v16.13.2/bin
     - /usr/local/bin
     - /usr/bin
     - /bin
     - /usr/sbin
     - /sbin
     - /usr/local/sbin