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While this was a major issue in the past (2G/3G era), as a rule of thumb, all modern phones (4G/5G) work everywhere these days. The 5G spectrum, for example, is split into over 100 bands, and while there's variation on what country/operator supports which particular one, the phones themselves are all built to support the whole lot.
The main thing is to ensure that your phone is unlocked in the country you buy it from, which is typically the case as long as you buy it outright from a third party instead of setting up a contract with a Telco.