New to me owner with red triangle

Hello everyone. I picked up a 2009 Prius a month ago with 272K miles on it, and now I have close to 275K miles. When I was driving the car on Saturday back from my nearest town(I'm in rural Texas), it all of a sudden threw up a red triangle about 4 miles from home, and I limped it home and parked it. It won't start up now, and using the OBD Fusion app on my phone I am reading these codes: P0137(an oxygen sensor, it threw this on Thursday last week and I haven't gotten a replacement ordered yet), P1121(it's been on and been low priority) and P0AA6. It seems that my app can't read the sub code on that last error and I think that's what's causing the issue. What would be the best move from here to get it back up and running? I typically do my own mechanical work and I'm experienced with DIY off grid solar for my house setup for what's that worth.

Thanks