Free and Open Source Software

Hi, I dont know if this is the right comunity to ask, please tell me otherwise. I apologize for my poor English, I'll try my best!

I'm a professional software developer with about 10 years of experience. I have only worked on closed-source enterprise projects throughout my entire career. I am not familiar with the workflow involved in FOSS projects.

Is there a guide that summarizes or documents all the information or standards you need to know to contribute to any FOSS project? This includes the standards for commit messages, tags, and how to propose a new feature or report a bug.

I understand that this may be basic information for many of you, but for me, it feels a bit overwhelming. Also, I think that I'm afraid of working on a codebase that I'm not familiar with. There is also a fear of my own code being judged online. You know, you can never escape imposter syndrome.

I appreciate any info, hopefully I'll be helping on improving some of my favourite apps in the future.