Lots of conferences have calls for talk submissions. Like this. Definitely go for those when you see them.

My general advice for tech speaking is to not bite off too much in one talk. Talk about something YOU think is interesting, scope it down to something you know you understand well, and frame it with something relatable.

It doesn't hurt to kinda "be out there" in the community a bit as well. Maybe write blog posts about the topic you're interested in speaking about. That way you're known as the person who knows about THAT THING. You're chances of being asked to speak are a lot higher that way.