As i am also one of the weird guys using (or better now: has been using) totally outdated tech for daily work for years now (especially an 520 ST), i cannot rec

As i am also one of the weird guys using (or better now: has been using) totally outdated tech for daily work for years now (especially an 520 ST), i cannot recommend one modern operating system more then Haiku. Haiku has everything i loved (and still love!) about the 16 Bit machines of the 80s / 90s (simple, snappy gui, incredible fast boot time etc.). I imagine if Atari or Amiga had survived the 90s, their OSes would look and feel like that.