Recently Google added support for VoLTE, WiFi Calling and 5G for Polish carriers.
Plus PL has 5G on the N1 and N41 bands. Google (the stock pixel OS) supports only the N1 band with Plus. My friend on the stock OS can use the N1 band perfectly fine, while I cannot connect to any one of them (5G is enabled in the SIM settings). NetMonster shows "5G • NSA • Disconnected!" and "Connection failed, not restricted by carrier".
I've heard that GrapheneOS uses a script to get the official Google carrier configuration, but here it is definitely different from stock.
Also, WiFi Calling (on Plus) doesn't work out of the box and I have to run https://github.com/kyujin-cho/pixel-volte-patch after every reboot.

5 days later

I don't know if that's allowed, but let's just bump this thread up