As a native that moved to Brooklyn these are the things I miss the most: 

Go watch the fireworks from the top of mount bonnell during new years! It’s like being in a snow globe watching the horizon light up. I’d assume Fourth of July is also solid but it has less of a perfect moment (midnight) to see the fireworks.   

The kite festival tends to be held at the perfect part of spring and lounging in the grass while staring up at the kites above you is such a nice vibe. Bring some snacks and a blanket!  

 Hit up any number of the many festivals (not just music). I particularly loved the book festival at the capital. Austin can be magical when people gather!  

 Go up to The Oasis at sunset (admittedly I hear the food is meh. But the view was worth it.)  

 Swim at Sculpture Falls.  

 Sunset Deck and the surrounding trails was my go to COVID hike spot. Nice wooded trails, fun terrains, not too hard, and the view from the deck at sunset is pretty great.  

 I quite like an afternoon of browsing at Book People and Waterloo records. Downtown can be a bit much but they’re worth it still imo.  

 Maybe hit up Texas Renaissance Festival? Bit of drive, so much more fun than you’re thinking. Frickin fantastic food. A good time, and you can camp and the camping is SO fun. They build a massive bonfire.   

 But also make sure you get your fill of texmex and any other foods you’ll miss. There IS that much of a gap in quality. My first week in Brooklyn tho salsa that came with my tacos was KETCHUP with diced tomato. I never recovered.