Hi,The android 12 developer preview 3 is packed with more carrier settings. All carriers in the Netherlands have support and they updated the expired apn settings. I found a carrier policy containing a very detailed list for europe with 5G support.
I suspect they are included with the upcoming may patch. I didn't expect Google tot fix this, a very pleasent surprise!
are you sure that it actually uses the 5G network - or does it just display it on the top line.
You should be able to check this with entering *#*#4636#*#* in the dialer (and check the output of 1st menu point (Phoneinformation or smilar).