How can I get assigned to work on open issues?

Quoting from another thread in the GSoC section:

Hey! Thanks for your interest — we always love contributions :slight_smile:
The decision if we will participate in GSoC 2021 and with which projects will only happen in a couple of month. We'll probably know more at the end of January; I can't promise anything right now.

And we generally don't assign issues to people not working for Elastic, since it gives the impression that they are blocked. If you have any questions, ask them on the issue and then create a pull request — you don't have to get the issue assigned.