You do realize that T-Mobile bought Mint earlier this year.

I actually picked mine up on Swappa for $690. At that price it was very competitive against other flagships. It might even go down a bit with the new Mark 5 coming out soon.

Yes and no. It has coverage on multiple 4G and 5G frequencies.
Check the first link and see what frequency you need in your are and then check the second link to see if it is covered. Where I am and where I mostly travel I need 5G band 71 and it picks it up beautifully.

https://www.cellmapper.net/map?MCC=null&MNC=null&type=undefined&latitude=0&longitude=0&zoom=11&showTowers=true&showIcons=true&showTowerLabels=true&clusterEnabled=true&tilesEnabled=true&showOrphans=false&showNoFrequencyOnly=false&showFrequencyOnly=false&showBandwidthOnly=false&DateFilterType=None&showHex=false&showVerifiedOnly=false&showUnverifiedOnly=false&showLTECAOnly=false&showENDCOnly=false&showBand=0&showSectorColours=true&mapType=roadmap&darkMode=false&imperialUnits=false

https://www.kimovil.com/en/frequency-checker/US/sony-xperia-1-iv

I might be a bit biased but I went for a Sony Xperia 1 Mark 4. Yes it is last years model but the performance is supurb. For me it was down to form factor. I tend to dislike curved or waterfall screens and Sony has stuck to truly flat screens. The second sticking point was expandable storage. Sony still has an SD card slot. I have 1.5TB of combined storage. The addition of an actual headphone jack and mechanical zoom lens were just icing on the cake.