If you don't mind the, uh, colourful presentation, the You Suck at Producing series (and channel with the same name) on YouTube is pretty good: https://www.youtube.com/watch?v=2kjCxfEZZKo - he also does pretty regular livestreams doing critique and analysis of user-submitted tracks.
If you're looking for a free wavetable synth comparable to Serum from the article, I recommend Vital: https://vital.audio - there's a fairly active community forum there as well.
If you're looking for a free wavetable synth comparable to Serum from the article, I recommend Vital: https://vital.audio - there's a fairly active community forum there as well.