Short answer: I suggest Gitlab as it includes everything project management needs for free, and you can even host it yourself should you have the need.
The reason is important--all the smaller tools out there being bought up by larger tools/companies and made into complete project management packages. It used to be that Github did just one thing--git hosting--and anything else was an "integration" with another service through an API, tokens and webhooks, etc.
Now what's happening is companies like Atlassian, Microsoft and Pivotal are buying or building all those little tools or services that used to be separate apps connected by happily sharing their API with anyone, and making them features of a larger product.
This isn't necessarily a bad thing. It means a lot fewer open browser tabs and less context shifts between one service and another.
I recommend Gitlab because it's both the most mature solution, free to use, and open source to boot. As Microsoft is still in the buying and consolidating stage, with some features in beta, Gitlab has had most of those features for years, and battle-tested them with their users able to report bugs or submit merge requests right on the very platform being developed.
The features included in Gitlab--for free--include git repo hosting on par with Github, unlimited private repos, issue-tracking and a Kanban board, CI (you can host your own runner or use their free runners), private Docker registry, artifact hosting, static website hosting, error-reporting, serverless and Kubernetes integration, wikis, code snippets and more.
So before you go use 1 or 2 services that will inevitably be rolled into some larger one, use the cheapest, most mature one out there that also happens to be open source. You may not need all the features now, but It's really cool when you realize they are right there waiting for you when you do, at no extra cost.
BTW: I'm a web and mobile developer, so don't know all the needs that game devs have that we don't from project management stuff.
