I, too have been unable to grow sunflowers - the chipmunks squeeze through my garden fence and eat them. Jerks. Thankfully my tomcat also squeezes through the bushes and eats them.. muhaha... I jest... He's a catch and release hunter.
But, there are plenty of things you can still plant right now in your zone! Even in pots. Most veggies *prefer* full sun but you'll find you can bend the rules a bit

I have a big garden but my favorite thing to grow are radish. They aren't fussy about soil, don't need fertilizer, can grow in part shade, and some varieties go from seed to table in less than 30 days.
It looks like for your zone, you can start your fall veggies around now. Any of the leafy veggies can take the part shade - kale, lettuce, beans, peas. You might try a cherry tomato in one of those felt grow bags. Sure, you wont get as many as you would in full sun... but you should get some. Especially if you start with a transplant from the garden store. Here is a planting calendar I found for you zone:
https://www.ufseeds.com/learning/planting-schedules/Zone-8-Planting-Calendar
If you just want a pretty plant, try Astilbe, begonias, mint, coleus, catnip, etc.