My experience with Fairphone 5:
Bluetooth:
Working in my car for receiving and sending calls. Works also connected to a Pebble watch.
GPS:
Works for me, it takes 10 to 20 minutes to get a fix, in the open air or at the balcony of my place (1st floor of a building 9 floors high). Sometimes it takes longer, if I don't see a fix in 20 minutes I restart the phone.
IDLE:
Using the current development image the battery lasts for the whole day, unless using Waydroid for too long. I haven't seen the background apps draining battery so far.
NFC
I use it with Waydroid in the transport system of my city, no issues.
Calls: No issues, 5G or Volte are working.
SMS/MMS: SMS fine, I don't use MMS.
Waydroid: Very fluid, but it hangs often when put in the background. Not a big deal because it starts in seconds.
Connection to PC: No issues to mount the device in Linux, or connect with adb.
Wifi/network: Disconnects if moving between WIFI antenna, but otherwise no issues.