Why are people so keen on having that network graph of forks? It's not necessary for collaboration. Status symbol?
If I want to fork your code and contribute back, that means I need to be on the same system as you.
There's a bunch of Gnome projects which require me to sign up to their specific git hosting service before I can contribute.
On most git servers, I have to fork in order to send a PR, which often means I have to create a fork on their system - which means I need to set up something to replicate it to my local machine.
It's all friction.
I'd love to see a project on (for example) GitHub and then clone it to my GitLab, work on it there, and send a PR from GL to GH.
You really don't. You just clone, code, commit, and send a patch (which is just one or more text files). That's it. You may just code and do a diff, if it's a simple fix.
The project may have a more complex policy to accept contributions. But a Fork and a PR is not a requirement.
How do I submit the patch to the repo on GitHub / GitLab / CodeBerg / whatever?
Presumably I need to hunt down the maintainer's email?