What mobility exercises do you prefer? Any particular routine you can recommend?

Start with The Odin Project: https://www.theodinproject.com/

It defers to FreeCodeCamp where beneficial but overall puts a greater focus on setting up an actual developer environment instead of doing everything in a sandbox. It's a bit more challenging for that reason, but overall better for your progression.

The Odin Project does go through React, but I'd actually recommend switching to FullStackOpen once you hit that point in the curriculum: https://fullstackopen.com/en/

Thanks for the suggestion. This looks like an excellent resource for beginners.

"Polyglot" refers specifically to language though. I've always taken it as someone being fluent in > 3 languages, following biligual and trilingual.

Based on your proposed alternatives, you're likely thinking "polymath".

So what exactly is wrong with these words in your opinion?

Super pedantic bit of feedback: Check the punctuation on your <p> level text. For example, the "sign up" section isn't punctuated, but the "invitation" and "join with a click" sections are. Same with "we sharpen our minds".