Moving from corporate to open source (need help/tips pretty please)

Hey folks, so I keep trying to find good info about this, but nothing quite gives me answers I'm looking for. Hope you guys can help.

I'm not a developer (UX designer/junior PM) and I'm leaving a corporate environment for open-source (or at least aiming for it) and I need some insight/tips.

I'm hoping to land a job at a certain company/project that is open source. They are lacking is UX processes and also their product development is rather chaotic/broken/inefficient. I'm hoping to introduce a bit of order to it and help resolve some ongoing problems. However I'm only vaguely familiar with open-source (only from afar) and I know these guys live on GitHub, which seems to me like a really chaotic/complicated/inefficient place to do project management (included research/design flow). I am new to GitHub too, so maybe I just don't know how to use it, but from what I've seen it's not tailored for that and anyone who is not a dev tends to feel lost there – and I would need it to be easier to use for non-devs too, but has to accommodate their needs as well.

I'm trying to learn and understand/think off what would be the best way to go about it. I can clearly see that they could use some of the standard "agile product development" processes, but they have their own ways of doing things and I don't want to/can't just swoop in and create a revolution, force them to use some platforms they won't feel comfortable with etc.

I was thinking about moving the workflow to GitLab which is somewhat similar to GitHub, just more friendly to everyone who is not a developer. A bit of a half way between GitHub and Jira. If you think it's a good idea, could you give me some arguments why it would be a good move (or not). Or any other tips in regards how to tame the chaos of open source product development that wouldn't be too forceful?

Anyone here with such experience? Could you tell me what worked and what didn't work?

Thank you so much for reading