My travel experiences with Apple devices and a few Android are, iPhones from the 12 models & newer will have most or all bands used internationally by foreign carriers. Android models such as many Motorola & Samsung models from the same era will also have the required bands, including 5G. The 5G service is not as common in most countries yet, but it is gaining, and is fairly common in Europe from my limited use.

I carry an iPhone 16 Pro Max and generally at least 2 Motorola Android phones, along with 2 iPads with 5G cellular service. I have the luxury of several free lines of service on a T-Mobile US plan that each get 5Gb of free high speed data roaming overseas. I think the sweet spot for iPhones is the 13 models, due to having both physical and esim capability, and decent cameras, screens, processor speed, etc. along with lower pricing on resale sites like Swappa. The 13 series and newer utilizes DSDS (Dual Sim, Dual Standby) and permits an IMS setup for WiFi calling versatility. That function has been discussed at length here on Flyer Talk.