The community edition is open source, the Enterprise edition is not.

I host my own gitlab-ce instance in docker which works well. I mainly needed a web UI for git and I track issues with it. I think there are boards or at least free plugins for the community version, but I do not use them. You can version your documentation in .md files too. Not sure if it can substitute Jira for you, but you mentioned Bugzilla and I like gitlab a lot more.

Just make sure to update the container regularly, you can’t make big version jumps without the intermediate updates.

I think you can combine it with OpenProject if you need more project planning.