I have set (on a Pixel 9) in settings under location: location services (wifi search and bluetooth search off, network location apple server, geocoder grapheneos proxy), SUPL GrapheneOS proxy, PSDS GrapheneOS server
With these settings it works for me in organic maps, pretty fast and accurate.
The thing with the arrow seems to be a thing of organic maps, but it disappeared after a while, i guess it needs to connect with satellites for a moment, whilst the other settings help to determine your current location faster.
If the arrow points in the opposite direction, just wave your phone around like painting an 8 for a moment and then it recalibrates.