Will my 4G LTE phone work after the 3G shutdown? It's from a niche brand, so it's not on the list

I own a Unihertz Jelly 2 smartphone. Unihertz is a small brand that makes niche phones, so I'm not surprised none of their products are on AT&T's list. Here's the band information for the phone (I don't know what any of this means): 

GSM: Band 2/3/5/8
WCDMA：Band 1,2,4,5,6,8,19
TDSCDMA: Band 34/39
FDD/TDD LTE：
Band 1/2/3/4/5/7/8/12/13/
17/18/19/20/25/26/28A/
28B/66
Band 34/38/39/40/41
CDMA2000: BC0/BC1

Can anyone tell me for certain 1) whether a phone with these specs should be affected by the upcoming shutdown? 2) If a phone is not on AT&T's list, does that mean it will certainly not work, even if technically its specs meet the requirements?

Thank you very much.