I'm good at Swift and native Apple stuff. I've given courses on it, in the past. I was actually shocked to find out that no one is really interested in that, out here. I could go into the city, but, quite frankly, I'd rather eat ghost peppers.
First, it sucks that you are facing that age discrim IRL. In the tech world, "doing talks" is a bit like publishing in scientific research. It builds a brand name for yourself and increases your value. This is why the young and aggressive (and mostly men) want to do it. Plus, it is a form of fame and adoration. The same group wants that too.
Second, I had a idea reading this post: Did you ever consider "doing a talk" with an audience of zero? Record it exactly like you are giving a talk, then post to your blog or YouTube. People would watch it; I know it. The difference: You couldn't mix with an excited, buzzing crowd after your talk, but maybe the comments section would be interesting. If you get lucky (great talk), it will pop-up on HN. For example, you said you are "good at Swift and native Apple stuff". Watch a few YouTube videos on the topic. Find areas of weakness. That is an easy way to generate ideas.
I enjoy writing, but don’t enjoy video production as much (but I haven’t really done enough to say that, definitively).
When I give talks and classes, I spend a lot of time, preparing. I spent close to a month, preparing this 90-minute Bluetooth class[1].
I have just been a bit strapped for time, lately.
Since you do bring experience, I would recommend (if you haven't tried yet), to give talks instead of just attending. I have found that the speakers tend to be well received regardless as they bring value. I did a lightning talk once and had the most positive interactions after my talk than any of the other meetups I attended.