Fossil is a free and open-source distributed software configuration management system, it also supports bug tracking, wiki, forum, email alerts, chat, and technotes into every created repository.
Ranked in these QuestionsQuestion Ranking
Pro DSCM + issue tracker + wiki
If you need a (distrubuted) SCM, Fossil comes with a built-in SCM, a wiki and issue tracker.
Pro Self-contained file
The data is stored in one single file. No file structure distributed over a bunch of folders.
Pro Multi platform
The executable is provided for multiple platforms, e.g. Linux, macOS, Windows.
Pro Easy to install
The Fossil application contains one single file. No need to install dependencies.
Con Ticket comments can't be edited
While a ticket can have multiple comments added to it, and (separately) also attachments — if the users have the right permissions — it is impossible to edit a comment after submitting it. This is probably why a comment must be previewed before it can be submitted.