Lots of people say Sourcehut, and I agree. It may not always be free, but I believe it's still free for OSS projects. All of the sourcecode is available, and the instructions for running your own servers is decent. It's been around for years, and I'd be surprised if it went down; it's never had an outage as long as I've been using it.

It has source repos, issue tracking, CI, mailing lists, and wikis. The pages are also lightweight, with little to no javascript.

You might find it ugly. It has no web-based PR/merge tooling (but has instructions on how to manage PR/merging using the mailing lists). It has a couple of restrictions on what kinds of projects you can host with gem (no cryptocurrency projects). It's a developer's tool, and built for people who have a fair amount of competency outside of web interfaces.

I love Sourcehut; I've been paying for it since before I needed to, and even though I'm not using it for commercial purposes... but it's not for everyone.