Runtime Bugs is a desktop-based bug/issue tracker written in Free Pascal and Lazarus. It is a simple application that saves all bugs in .bugs files, stored in a text-based format that can be placed inside version control repositories. It is mainly meant to keep track of bugs and issues for small, mainly personal projects since it doesn't keep track of any user or date information.
Each issue can have a type (group, topic, task, bug, request), a state (todo, wip, implemented, done), priority (blocker, high, norma, low) and optional sub-issues. It does not enforce nor require any sort of workflow beyond that and the assumption is that this information (perhaps coupled with the full text search) should be enough for most uses.
You can download Runtime Bugs from here:
To run Runtime Bugs you need at least Windows 2000 (note that currently the installer does not work in Windows 2000, use the second download link with just the executable and make the file association manually) or Linux with GTK+ 2 libraries installed (any distribution since 2015 or so should work fine). You may also be able to build the source code for macOS, but my iMac is too old to run the latest macOS to try out.