MarsSeed [1] filed a deletion request for ruby-lint [2]: EOL Ruby 2.x linter from 2016. Not compatible with current ruby 3+ and the corresponding ruby-parser 3+:

$ ruby-lint /usr/lib/ruby/3.0.0/rubygems/specification.rb:1453:in `rescue in block in activate_dependencies': Could not find 'parser' (~> 2.2) among 88 total gem(s) (Gem::MissingSpecError) Checked in 'GEM_PATH=/home/user/.local/share/gem/ruby/3.0.0:/usr/lib/ ruby/gems/3.0.0' at: /usr/lib/ruby/gems/3.0.0/specifications/ruby-lint-2.3.1. gemspec, execute `gem env` for more information from /usr/lib/ruby/3.0.0/rubygems/specification.rb:1450:in `block in activate_dependencies' from /usr/lib/ruby/3.0.0/rubygems/specification.rb:1439:in `each' from /usr/lib/ruby/3.0.0/rubygems/specification.rb:1439:in `activate_dependencies' from /usr/lib/ruby/3.0.0/rubygems/specification.rb:1421:in `activate' from /usr/lib/ruby/3.0.0/rubygems.rb:286:in `block in activate_bin_path' from /usr/lib/ruby/3.0.0/rubygems.rb:285:in `synchronize' from /usr/lib/ruby/3.0.0/rubygems.rb:285:in `activate_bin_path' from /usr/bin/ruby-lint:25:in `<main>' /usr/lib/ruby/3.0.0/rubygems/dependency.rb:313:in `to_specs': Could not find 'parser' (~> 2.2) - did find: [parser-3.1.3.0] (Gem::MissingSpecVersionError) Checked in 'GEM_PATH=/home/user/.local/share/gem/ruby/3.0.0:/usr/lib/ ruby/gems/3.0.0' , execute `gem env` for more information from /usr/lib/ruby/3.0.0/rubygems/specification.rb:1451:in `block in activate_dependencies' from /usr/lib/ruby/3.0.0/rubygems/specification.rb:1439:in `each' from /usr/lib/ruby/3.0.0/rubygems/specification.rb:1439:in `activate_dependencies' from /usr/lib/ruby/3.0.0/rubygems/specification.rb:1421:in `activate' from /usr/lib/ruby/3.0.0/rubygems.rb:286:in `block in activate_bin_path' from /usr/lib/ruby/3.0.0/rubygems.rb:285:in `synchronize' from /usr/lib/ruby/3.0.0/rubygems.rb:285:in `activate_bin_path' from /usr/bin/ruby-lint:25:in `<main>'

[1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/ruby-lint/