Why not work on UpWork & co? I don't think they ask you anything about your age (cough real age cough). After all, On the Internet, nobody knows you're a dog [1] ;)
Additionally, you can work on various open source projects (either by your own or just contribute to existing ones) and build some brand awareness too.
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[1]: https://en.wikipedia.org/wiki/On_the_Internet,_nobody_knows_...