Thought I might help out with a few unanswered questions here:
Slickcraft: Big difference between the S9 and S10 is the support for Band 12. 13, 17 & 18 Most of the larger providers have picked up an allotment for these bands, it is in the 700MHz range. Much better building & foliage penetration. For example see this chart for a generalization of what providers use what band:
https://www.droid-life.com/2015/02/0...print-tmobile/
Verizon degradation: I don't know the model number of each of everyone's phone, but it was mentioned that Verizon is upgrading to 5G. Most towns limit the number of sector antennas a provider can have. It is possible Verizon is removing some of their higher frequency sector antennas to put in a sector their 5G will be compatible with, assuming their 700Mhz band will cover the loss of this sector replacement. Check out what bands your phone supports vs the provider above.
TMobile coverage: I have them, they work real well in Moultonboro. Going out 171, coverage ends at Tuftonboro 4 corners and resumes the closer you get to either: the lake, Rt 16 or Rt 28 (big dead spot). Center Harbor and Meredith are reasonable, down Rt 3 and 104 work for the most part. They don't seem to have a local roaming partner, unfortunately, so their dead spots are well, dead.
Network extenders: I have one, TMobile will give you one free ($25 deposit) if you have an account with them. I can get 1,000 feet from my house, before it jumps off onto a regular TMobile cell. Also, the TMobile extender will hand off to a tower or wifi, it is like a real cell site in your house.
LTE: As many know, I'm sure, LTE is for data only. There was a discussion on this thread of VOIP over wifi, many provideres and many phones support this. There also exists VOLTE, that is voice over the LTE network. Both your phone and provider must support this. Verizon supports LTE on many towers and if your phone doesn't support VOLTE, you might have a dead spot, whereas the Verizon map says you don't.
Cellular is a very dynamic arena.... some providers are rolling out 600MHz, TMobile has one in Maine on the NH border, but I can't get it at my house, lol