Aaaaand my Unlimited Plus Subsidy plan, which I got well under a year ago, doesn't work with TNX. I can either switch to one of the more basic plans (nonstarter due to hotspot allotments/speeds) or spend an advertised $15/mo more to go to the standard Unlimited Plus plan. Think I'll wait instead and complain every so often 'til TMo devices it's worth it to get me on their 5G network more often.
Got my (unlocked, directly from Samsung) S21 in at 3:50p today, along with the Qi charger (which includes a 25W wall charger!) and Buds+.
The Sprint SIM from my S20 worked fine in the S21, though when activating I was prompted with an "are you sure you don't want to get a T-Mobile SIM for this?" message, probably because I'm on TMo towers 100% of the time when in Austin (if I was in Fredericksburg it'd be majority 312-250).
Seems like the radio in the S21 is a bit stronger; I'm at the edge of n41 coverage at my kitchen table and was able to pull a few Mbps more than I recall getting on the S20. Additionally, upload speeds seem better on n71; was able to hit 40 Mbps pretty easily where the S20 would hit 30-35.
I'm not seeing NR CA, but I'm not sure whether that's a limitation of the Sprint SIM or whether it just hasn't been turned on here.