Where we live just doesn't have good signal, and With AT&T I have to turn LTE off on all my iPhones to be able to walk the dog in the neighborhood and not lose a call on my Xs Max. Neighbors with Verizon and T-Mo have the same issues - we are too close and just below the cellular towers on the mountain for them to radiate signal down to us.
In our house, right up against NORAD road, we only have 1 bar of signal on any of our Qualcomm iPhone 7, 7+, 8, and X, and iPad mini 4. Same with my Intel Xs Max = only 1 bar. Speed and connectivity on everything sucks, at usually 0.75 - 1.5 mbps, rarely 3-4mbps.
Only my iPad mini 5 has 2 bars of LTE, and right now my LTE is running about 7.8 mbps download, and 0.46 mbps up. My 7+ with 1 bar of LTE is about 1 foot away from the iPad and it's only getting 0.29 mbps download at the same time.
I'm stuck in the Apple ecosystem.
[EDIT - now the 7+ gave me 2.67 mbps on 1 bar LTE when I wasn't testing speed at the same time as iPad LTE. My Xs Max won't connect to LTE right now, but got 2 bars of 4G and ran 2.36 mbps. 1/3 the speed of my iPad mini 5.]