Issue trackers in early-stage projects

Hey! This is a question for anyone who has started/released an open-source project, scaled a personal project or has started a startup with a small technical team (could also be solo).

I am primarily interested in your use (and lack of use) of issue tracking systems. My questions are:

• How did you track work at the start of the project?
• If not from the start, when did you transition to a more formal/structured method of issue tracking?
• When you made that jump – what was the tool and why did you choose it?
• Did you specifically avoid any tools, if so why?
• Finally, did you have any further iterations of your issue tracking tooling?

Feel free to mention anything else you think might be interesting. For context, I am interested in the motivation behind the selection and transition of early software teams to use issue tracking tools.