T-Mobile is paying customers to swap out their Sprint SIM cards
SIM card & eSIM | T-Mobile Support
SIM card & eSIM | T-Mobile Support
USA Activation Sim Card Verizon AT&T Sprint Xenon iPhone 6S 7 8 X XS 11 12 | eBay
You can now self activate t-mobile SIM to TNX program from Sprint.com website. I have successfully activated it on Samsung Galaxy A71 today using t-mobile R15 sim card. Download t-mobile App experience