Graphite
I don't want to get into the ongoing debate about Aurora Store security and/or privacy, just offer my opinion. Many users here are far more knowledgeable about that than I. Remember, you unlocked your phone's loader to install GrapheneOS and there are a heck of a lot of brilliant people working on this project and everyone is going to know about malicious software immediately. Even if you stick with a stock GOS, then you would be worrying about GOS updates. This is the best you are going to get and, still have a usable cell phone, stock, source code apps or side loaded apk's.
As far as downloading from Aurora Store goes, here is how I have always achieved success on every app I've wanted: Use it on off hours like 4-6AM. Lots of times the search function won't work for me at all or return results for a half-second before telling me that I'm using a time limited connection. Sometimes, if I'm sure of the app I want and keep getting the half-second shuffle I search a bunch of times until I get the timing just right to click on the app before it disappears. Once you got it it always installs. And one final thought: I downloaded Gcam and Gphoto and Gmaps no problem from Aurora Store. No Google services at all are needed to run them. Occasionally I need to restart my phone for Gmaps to give directions but other than that they all 3 run fine in my owner profile with no Google at all