Forge is a software suite for [software] project development. Well-known forges are Gitea, Sourcehut, GitHub, GitLab, GNU Savannah.
GitHub has the most users, has the best user interface and great a11y. It is also respected by normies. There is a common joke that programmers share their GitHub profiles upon acquaintance. Imagine if a person (such as an HR) expects you to have a ‘good’ profile, but you respond that you post your code to federated Gitea only. From the ethic point of view, GitHub is really bad. Especially with that Copilot thing.
GitLab is like GitHub, except it's worse in every possible way. The UI is worse, there are less users, and it's just as unethical. I am talking about the main instance. If you self-host it, it's a different thing!
Gitea is a fork of Gogs. I kinda dismiss Gogs. Gitea is where stuff happens. It's like GitHub in UI, but a11y is reported to be much worse. They are working on federation, I really respect that. I expect Gitea to become the best choice, once the federation is on. There is also a big instance of Gitea based in Germany: https://codeberg.org.
Sourcehut is opinionated, I respect that. It has cute UI, but is overall hard to use. It has the best ethics and good a11y. Do you know what I dislike? That's email and hardwrapped plain text. Sourcehut focuses on that. Argh. They offer a good IRC service that I use though.
They call me to abandon GitHub. Would be great.