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Sysadmins slam Apple’s SSL/TLS cert lifespan cuts
(www.theregister.com)
This is a most excellent place for technology news and articles.
I have just dumped code into a Chrome console and saved a cert while in a pinch. It's not best practices of course, but when you need something fast for one-time use, it's nice to have something immediately available.
You could make your own webpage that works in the browser (no backend) and make a cert. I haven't published anything publicly because you really shouldn't dump private keys in unknown websites, but nothing is stopping you from making your own.
Any machine I'm on has Python installed, so that's my go-to.