Hi lauraingram! Your teacher should have a list of options you can choose from, or if you really wanted to choose your own topic, I'd suggest you think about what your interests/concerns are, and what you've read about it in the last 9 months.
For example, if you're an animal lover - something about lockdown puppies or the rise of illegal breeders could be interesting. Or if you're very worried about VCE and your ATAR, maybe something about universities broadening their admission processes. If you're concerned about the environment, something about medical waste during covid would be fun. Or if you're into sport, I can think of a certain joker who has ruffled a lot of feathers very recently

Whatever topic you choose, just make sure it's been covered by multiple Australian media outlets since Sept last year and you'll be fine! I've got a short video here about what to research for a speech if you're interested:
https://youtu.be/lUuE06DNlFI