Udemy is full of different courses. Lots of good free content as well as paid.

I also frequent reddit and subscribe to subreddits that relate to the topics I want to learn more about.

Wikihow is also a great place if you're looking to learn one thing at a time.

I generally stick to some academic reading either on iBooks or scientific American website archives. Another great way to learn about new things is through up-to-date podcasts on breakthroughs in different fields.
In terms of apps I would say that elevate is a great one for broadening your mind in maths and English or even duolingo if learning another language is something you are interested in doing.

I like to use Duolingo app for languages. For manual skills I prefer youtube tutorials to books. They are shorter a easier to find which makes them more appealing for me.