Meanwhile, a company I used to work at keeps on using self hosted MantisBT.

Its maintenance takes like 2 engineer days per year total, if that. Its initial setup with all the plugins ( of note are those for project management and release tracking) and integrations (e.g. git) took one engineer week if I remember correctly.

And it works just fine for 7 years now, to the point that the only advantage of Jira I see is a slightly fancier looking interface for the regular user. Whilst costing peanuts.

I even prefer the old school Mantis BT look and feel.