I use JIRA for my day work and GitHub Issues for my open-source projects. I'm a long-term JIRA user (and even somewhat evangelist). There are probably many muc

I use JIRA for my day work and GitHub Issues for my open-source projects. I'm a long-term JIRA user (and even somewhat evangelist). There are probably many much more "modern" issue trackers over there, but JIRA worked extremely well for me for many years. There are a few big problems with JIRA, though (field-level security and limited issue hierarchy). For my OS-projects I've found GitHub issues to be more than sufficient. That's what I'd call clean and simple.