I admire the de-Googled approach of GrapheneOS. As a lawyer, privacy concerns resonate with me too. I love the rebellious attitude of tech that presents an alternative choice in an overly duopolistic market.
That said, I wouldn't last 8.4 months like the author. Even though he admits to some Google app usage, I'm in too deep — I'd never be able to get out. But if I get the chance, I'd like to try it on a secondary phone. Those solid black icons are one reason. They look cool.
Graphene supports the 6a, which unlocked goes for ~$100 on ebay. I imagine you can swing that as a lawyer to play around.
I'll also echo the ideas from everyone else here. You can just use it as a normal Android phone the way you do any other and there's still big benefits. There's also really big benefits in terms of carrier privacy that aren't often talked about, like vpn routing and hotspot usage.
you can use mostly google appsand still benefit (e.g. unlike google android, play services aren't privileged and are sandboxed like any other app) https://grapheneos.org/features#sandboxed-google-play
also you can restrict some apps network permissions, for example i use the google camera app with the network disabled :p
Not wanting to discourage you from trying Graphene, but the icons are probably not a good reason. Can always install an alternative launcher and icon pack on stock android.
Running Graphene for a long time now, everything works perfectly fine, but I don't do mobile banking.
my take on this is to some advocates probably shocking. But I think you don't need to perfectly switch and never touch anything google again.
I personally just encourage people to take a look at what you are using, and if you could gradually change some of it. Who knows sometimes alternatives even offer better services. I am not saying never use anything google ever again. Just question your tools regularly and peruse the alternatives.