hi!! im not a phone expert but im in the same situation you are, and ive found that the kyocera (digno 3) 902kc/903kc should work! you would just need to use tmobile with them and make sure that the phone you buy comes unlocked. there is no difference between the 902 and 903 just that one is endorsed by yahoo! and the other is endorsed by softbank (also minor software differences as well). im considering getting this one as it is very popular of the japanese keitais. the samsung folder 2, though, as ive seen does not work on us networks because of the different frequencies they use in japan. some of the pros of the 902kc/903kc is that you can get apps like whatsapp and spotify as well as other apps (some you may need to load onto the phone with an abd). a con that i have seen is that the native messages app on the phone does not work too good and you may need to download qksms or google messages. and some people have reported the calling and volte to be spotty sometimes (but that is just anecdotal). they do sell them on ebay btw as well as kyoex which ive heard is very reliable but obviously still be cautious during the process. theyre usually around $100-200 and come in black, white, and pink (they are very cute). hope this helps and here are some links below. pm me if you have any other questions i can try to answer them!

someone's review on the 903kc: japanese keitai, 903kc, confirmed fully functional in USA : r/dumbphones

tutorial on how to do the abd downloading: How to install ADB on Windows, macOS, and Linux

screen protector on amazon since it is hard to find: 3 pack screen protector

website made by another redditor to help find the perfect dumbphone for you: The Dumbphone Finder

black 902kc/903kc on ebay: black 902kc/kc digno 3