T-Mobile Network Pass allows you to try T-Mobile's 5G data network for up to three months for free, while keeping your existing service with your current carrier. All you need is an unlocked, eligible eSIM-capable phone, and to download the T-Mobile app from the Apple App Store or Google Play store. Then you can experience unlimited high-speed data on the T-Mobile network, all with your own phone, phone number, and apps.
Doesn't need a credit card, no need for planning ahead (just download the app and away you go), no physical sim (you do need an eSIM phone).
Basically this just became the traveller's choice for phone data plan when visiting the US.
update: confirmed as unlimited talk, text, and data
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Limited-time offer; subject to change. 5G device req'd to access 5G network. Data available for 3 monthly cycles for approximately 90 days. During congestion, customers on this plan using>50GB/mo. may notice reduced speeds until next monthly cycle due to data prioritization. Video typically streams on smartphone/tablet in SD quality. Tethering not available. Not for international use. Active non-T-Mobile service required; your carrier's terms also apply. You may need to upgrade when you switch to get full coverage. Coverage not available in some areas. Not for international use. See Network Management Policies and Terms and Conditions (including arbitration provision) at T-Mobile.com for additional information
Any requirements such as US ID or anything like that?