I'm a former frontend developer (JS, CSS3, Bootstrap etc.) with some OOP PHP experience. I've built a fully functional Magento 1.9 site with 80K products and built a smaller site with Magento 2.1 although the theme was not mine.
It's been a couple years break from web development and I've noticed a lot has changed with M2. Adobe acquired it, no more installation wizard, ElasticSearch is required etc.
I read a lot of people mentioning the Magento U courses for learning but those are incredibly expensive. Are there folks who are learning for free just by exploring the code base and asking questions when stuck?
How should one go about brushing up on PHP 7, Magento 2.4 and everything in between if you're poor?