(Please note that this might be an XY Problem question but written this way to make it brief).
Briefly, I was GSoC24 contributor at Chromium WebXR and I would like to contribute to Swift. Went to search for public projects and the first place that can in my mind was GSoC. So, if I cannot contribute to those projects as a non-gsoc contributor, where can I find other open projects that I can do so?
Please let me know if there is a better place to ask this question.
In theory you could work on these projects... I would suggest waiting until we pick projects that will be active this year and after that you could work on some of the ones which were not picked up maybe? It'd be a waste to duplicate work with an accepted GSoC project -- and we would want to support and make successful the GSoC student of course, which could mean your work not getting used as much or even not merged if "someone else is doing it now" etc.
You can also search github for "good first issue" tagged issues. Those would be great because they're usually small in scope, while gsoc projects can take many weeks to complete.
If you'd like to pick up any of these you can ping here and we can try to find someone to point you in right directions (or just ping on the github issue).