Awesome Code improves your code readability by git push or sending pull requests, with one click or even fully automated. It’s an online rubocop -a service.

Codacy checks your code from style to security, duplication, complexity, and also integrates with coverage. Codacy is free for open source, and it provides RuboCop analysis out-of-the-box.

Code Climate provides automated code review for test coverage, complexity, duplication, security, style, and more, and merge with confidence.

CodeFactor reports various code metrics like duplication, churn, and problems for code style, performance, complexity, and many others. CodeFactor is free for open source. It supports analysis and autocorrection for RuboCop.

Codety detects code issues for 30+ programming languages and IaC frameworks, Codety Scanner is open source and it embeds 6,000+ code analysis rules(including RuboCop rules).

Hound comments on style violations in GitHub pull requests, allowing you and your team to better review and maintain a clean codebase. It is open source software.

Pronto does quick automated code review of your changes. Created to be used on GitHub pull requests, but also works locally and integrates with GitLab and Bitbucket.

ReviewDog is similar to Pronto but with better support for GitHub Actions.