About three weeks later: I'm afraid that no one can actually comment any essential resources. Or they simply don't bother (not blaiming, I really get it).
From what I gathered:
- Kratky method
- the wiki for /r/hydroponics has a rather verbose gettino started guide. Still a bit word-y and not too dense in information
- "epic gardening" is a bit cringe "join my class" but generally some good info
- if you buy (or can get) the stuff anyone else uses: the three kinds of fluid fertilizer, or the "general hydroponics" stuff, you can just follow your guts and try the things they claim on the internet (google-skills still required)