Apple
Does the iPhone 6s / 6s Plus support eSIM?
No, the iPhone 6s / 6s Plus has no eSIM and only works with a physical SIM.
The iPhone 6s / 6s Plus does not have eSIM. For mobile data abroad you will need a physical (travel) SIM with this device, or roaming from your own provider.
Source: GSMArena
Check your iPhone 6s / 6s Plus for an eSIM yourself
Dial *#06# on your phone. A 32-digit EID number means your phone has an eSIM. On iPhone check Settings > General > About; on Android check Settings > SIM manager.
Frequently asked questions about the iPhone 6s / 6s Plus
Can I use an eSIM on the iPhone 6s / 6s Plus?
No. The iPhone 6s / 6s Plus is not eSIM-compatible and only works with a physical SIM. For mobile data abroad you'll need a physical travel SIM with this device.