All bug trackers seem to be too complicated, so I made one myself in less than 300 lines. I imported the issues from GitHub and it seems to work well in #Dillo and #links2.
https://bug.dillo-browser.org/
Issues are stored in plain Markdown files with some special headers in a git repository. They get rendered to HTML when pushing a new commit to the bugtracker repo.
The whole thing is less than 300 lines of shell script and awk. It uses no javascript or databases.

The source code of the previous issue, showing simple headers and markdown syntax.

A issue rendered in Dillo with the headers and code fences for snippets.

The same index page rendered in links2

Main bug tracker index page rendered in Dillo