I’m having the same issue on my brand new 15 Pro.
I upgraded from the X, and had the same issues on it but thought the upgrade would help. Nope. Still showing 1-2 bars on the LTE network instead of 5G. I’ve checked all my settings as per this forum. I have not attempted an eSIM yet as it seems only some people are having success.
Right beside me my husband has full bars on his Android. I’m on an offshoot of the same provider as him but they insist they do not throttle (in fact say that it is not possible to) so I am technically on the exact same provider.
Is this a problem then with the 15 itself? Should I have bought a 13 or 14 instead? I thought newer would be better.
I have Apple everything so stuck with it as it all syncs together but this is making me think about my next purchase. Might be switching to android.