Quickest way to find out: dial *#06#. If an EID number appears alongside your IMEI, your phone supports eSIM. You can also check under mobile network settings for an option like Add eSIM or Add data plan. Broadly, iPhones from the XS/XR generation onward, Google Pixels from the 3 onward, and Samsung flagships from around the S20 support eSIM, along with many recent mid-range models, but regional variants differ, so verify your specific unit rather than the model name.
If you have eSIM support, activation abroad becomes trivial: buy a plan online, scan a QR code, and you're connected, sometimes before you even land. Most eSIM phones also still have a physical slot, giving you the ideal dual setup of home SIM plus travel eSIM.
No eSIM support isn't a dealbreaker at all. Physical tourist SIMs are sold at airports, carrier stores, and convenience stores nearly everywhere, and are often cheaper per GB than travel eSIMs anyway. The only real loss is convenience on arrival.