I think that ageism might be less of a problem than you think. While it certainly exists at companies that have a certain culture, I've generally worked for companies that explicitly reject "Valley Culture" and we often try to hire older engineers. The difference in experience, work ethic, and overall attitude is huge and positive. I'm the second youngest engineer at my current (small) company at 31, and it's great.

Your main barrier is experience, but if you're willing to go for a junior level position, that shouldn't be an issue.

So generally, look for companies with a more mature culture - avoid buzzwords like "rockstar" and "ninja" (secretly, everyone should do this), steer clear of "unicorns", and read the bios on a companies website, and you should be able to find a good fit.