Hercules-ing a Spaceport into play saves quite a few Turns. Heroes are goofy.
If you want to see the Nalanda upper limit, that map I included is about as perfect as it can be and is a straight-RNG map. The only reason why I didn't finish the tech tree sooner is because I Scouted eastward instead of westward initially. Knowing the map, it might even be faster to move your initial Settler to Piopiotahi for the free Culture to get you to Amani even faster.
CivVI is now official dumb. Future Tech in the Ancient, anyone?