This is an area I'm pretty passionate about.
So first of all, it's pretty clear that you _do_ have some interests. You mention Feynman and Kazantzakis. That sounds like you're interested in the history of science and literature. That sounds pretty cool.
Many people will recommend going to a professional which I won't try to dissuade you from but that's not mutually exclusive with examining your lifestyle.
I'm obsessed with this podcast by Andrew Huberman (Stanford Neuroscientist) because he's talking about a scientific basis for stuff that has "felt" true to me for a while. Your food diet affects how you feel but your information diet does massively as well. There is a neurochemical basis for this with your baseline dopamine levels, that sets your motivation.
https://www.youtube.com/watch?v=QmOF0crdyRU&t=779s
I also recommend reading the book Dopamine Nation.
Too much social media will fry your brain. If you're checking Hacker News more than a handful times of day, work on doing less of that. If you're addicted to Reddit, Twitter, or pornography, work on doing less of that. Exercise. Spend time in the outdoors. Focus hard on sleep hygiene. Eat less sugar and processed foods.
You can not change all this stuff overnight but if you can take baby steps it will help massively. You will not feel better tomorrow or next week but if you take tiny steps you will feel a tiny bit better in a few months.
I would also highly recommend learning about mindfulness, meditation, and yoga. A lot of dissatisfaction is aversion to a feeling of emptiness that we have to learn to accept.
Again, I'm not trying to dissuade you from getting any sort of help, especially if you're socially isolated (though you mention having friends). I just don't want you to underestimate how much you can help yourself.
Lastly but not least, if you're eating great, exercising, getting natural sunlight, spending meaningful time with good social relationships, sleeping consistently, and moderating your internet usage, and you still feel no energy or interest in anything, you can just calmly accept it. Life "passes" us all by whether we're joyful or interested or not. Sometimes people with passionate interests actually get more problems from those interests than someone who can just calmly accept the moment for what it is. Ask yourself if the interests would make you happier, or if the actual problem is that you are making an imaginary problem out of not being interested in things. Just food for thought!