Firstly, it's great that you're looking to contribute to open-source projects. It's a fantastic way to learn and grow as a developer. If you're finding that many of the "good first issue" tags are related to Dart and you're not comfortable with that, there are still plenty of other options available.

Here are a few repositories that have issues labeled as "good first issue" and are welcoming for beginners:

1. Microsoft Terminal (https://github.com/topics/good-first-issue): This is the new Windows Terminal and the original Windows console host. The main language used is C++.
2. First Contributions (https://github.com/topics/good-first-issue): This repository is specifically designed to help beginners contribute to open-source projects.
3. Files (https://github.com/topics/good-first-issue: This is a project for building the best file manager for Windows. The main language used is C#.
4. Responsively App (https://github.com/topics/good-first-issue: This is a modified web browser that helps in responsive web development. The main languages used are JavaScript and React.
5. Refine (https://github.com/topics/good-first-issue): A React Framework for building internal tools, admin panels, dashboards & B2B apps. The main languages used are JavaScript and TypeScript.

You can also visit github.com/topics/<topic> to find projects related to a particular topic that interests you. For example, if you're interested in machine learning, you can visit github.com/topics/machine-learning to find relevant projects and starter issues2.

Remember, the goal is to learn and grow. Don't be afraid to pick up an issue even if it seems a bit challenging at first. The open-source community is generally very supportive and there will be people willing to help if you get stuck. Happy hacking! 😊