Google Fi is better than T-Mobile for international travel for one big reason: 4G data. I’ve been using Google Fi since January 2018, after two years on T-Mobile. In 2019, I also purchased a laptop with a SIM card slot, and installed a data-only SIM from Fi. Getting a SIM to work on Windows requires a few additional clicks compared to a phone, but it’s fairly straightforward. If you’re not interested in those phones, and your current phone isn’t compatible, you’re out of luck.